FR2868637A1 - Contents e.g. isochronous data, storage managing method for e.g. domestic audio-video network, involves managing number of copies for each content stored on set of storage units, according to duplication/deletion policy of copies - Google Patents

Abstract

The method involves managing the number of copies for each content stored on a set of storage units, according to a duplication/deletion policy of the copies. The managing of the number of copies includes modifying the number of copies by duplication and/or deletion, to maintain a difference between a simultaneous access number and a maximum simultaneous access number. Independent claims are also included for the following: (A) a computer program product comprising instructions for executing contents storage managing method (B) an information storage unit (C) a device for managing storage of contents (D) a node of a communication network with a contents storage managing device.

Description

A method and system for managing content storage in a network, based on

  on taking into account the number of copies of these contents.

  FIELD OF THE DISCLOSURE The field of the invention is that of data communication networks. More particularly, the invention relates to a method for managing the storage of isochronous data in such a network.

  Today, communication networks are known to which different devices generating and / or receiving isochronous data contents are connected, as well as storage units for these contents (external hard disks for example).

  The invention applies in particular, but not exclusively, in the case of a home audio-video network, where the isochronous data stream carries audio-video (AV) type data.

  2. Solutions of the Prior Art Typically, each storage unit is an audio video hard disk. It is clear, however, that the present invention also applies to more complex storage units, each of which may comprise several audio video hard disks and control means thereof.

  The invention applies particularly, but not exclusively, in the case of a heterogeneous home audio-video network comprising a backbone network comprising nodes to which equipment is connected, directly or via sub-networks. These sub-networks are, for example, IEEE 1394-compliant buses. It is recalled that the latter is described in the following reference documents: IEEE Std 1394- 1995, Standard for High Performance Serial Bus and IEEE Std 1394a-2000, Standard for High Performance Serial Bus (Supplement).

  Indeed, in the IEEE 1394 world, we can now find AV / C-compliant external audio-video (AV HDD) hard disks (described in the following reference documents: AV / C Digital Interface Command Set General Specification Version 4.1 2001012 and AV / C Disc Subunit Disk Drive Device Type (# 2001023)). They are mainly dedicated to the storage and playback of audio video streams (storage & playback). They can process several flows simultaneously (or competitors): for example an incoming flow (storage) and an outgoing flow (restitution).

  We will now briefly present, through an example and in connection with FIG. 1, the current technique of storing and rendering contents, in a heterogeneous home audio-video network as mentioned above.

  Consider some sources and / or audio-video receivers (AV) compatible with the IEEE 1394 standard and interconnected via IEEE 1394 buses themselves interconnected via an AV backbone 10. The backbone AV 10 of this figure 1 comprises: a unit switching center 11, network adapters (or nodes) 121, 122, 123 and 124 providing input / output interfaces (for example IEEE 1394 interfaces, infra-red receivers, etc.) and control means ( eg network remote control managers, data flow managers, graphical user interfaces, etc.).

  A and B are digital TVs (both source and receiver), D1, D2 and D3 are AV / C hard drives with simultaneous input (or write) access capabilities and simultaneous access capabilities ( or competitors) output (or read) restricted. For example, the Dl and D2 hard drives are capable of managing up to two simultaneous streams: an input stream (storage) and an output stream (read), while the hard disk D3 is able to handle up to three simultaneous streams: one input stream (storage) and two output streams (read).

  The input streams are each represented with a downward arrow 135, 136 and 137 while the output streams are each represented with an upward arrow 131, 132, 133 and 134.

  Each hard disk (Dl, D2 and D3) is controlled by a control module (SW1, SW2 and SW3) placed in the network adapter (124 for SW1 or 123 for SW2 and SW3) to which the hard disk is connected ( by means of bus 1394).

  We put ourselves in the following context: a content c was previously stored in the hard disk Dl. The reading on the hard disk D 1 of this content c is triggered by a first user, the content c being displayed on the television A. While the first user has already started reading the content c, a second user wishes to trigger playing the same content c, stored in the hard disk Dl, and display it on the television B. The problem is that the second user can not access the content c stored in the hard disk D 1. Indeed, the content c stored in the hard disk Dl can be read only once at a given time since the hard disk Dl has only one simultaneous read access.

  Thus, a major disadvantage of this type of data network 10 is the relatively high frequency of occurrence of conflicts (the consequence of which is the impossibility for some users to read a content) related to the presence of several users and to the capacity of the user. limited simultaneous access of hard drives D1, D2 and D3.

  To try to solve this problem, we know a technique called mirror copy (or mirroring in English). This technique is, for example, described in US6442551. It is also the basis of the RAID system (Redundant Array of Independent Disks and English redundant independent disk array). This technique is based on an identical copy of all data from one hard drive to another hard drive.

  In the example mentioned above, the mirror copy of the hard disk D1 on the hard disk D2 for example would allow the second user to access the content c stored on the hard disk D2 regardless of the use of the hard disk D1 by the first user.

  However, this technique is cumbersome to implement. It requires copying the entire disk D1 and not just the content c. Thus, it is consuming in time of copy and space in the hard disks.

  3. OBJECTIVES OF THE INVENTION The invention particularly aims to overcome these disadvantages of the prior art.

  More specifically, an object of the invention is to provide a method for managing the storage of contents in an isochronous data network comprising a plurality of storage units, said method making it possible to optimize the use of the storage units while reducing the risks. the appearance of a blocking situation in which a content could not be read by one of the users.

  It is another object of the invention to provide such a method which is of low consumption in time and in storage units.

  Another object of the invention is to provide such a method which is simple to implement and inexpensive.

  Yet another objective is to provide such a method that requires a low or no user intervention (that is to say that is almost transparent or transparent to users).

  4. ESSENTIAL CHARACTERISTICS OF THE INVENTION These objectives, as well as others which will appear subsequently, are achieved by means of a content storage management method, each comprising isochronous data, in a communication network. to which at least two storage units are connected.

  According to the invention, such a method comprises a step of managing a number of copies of each of the contents stored on all the storage units, which is a function of a duplication policy / deletion of copies of contents.

  Thus, the invention is based on a completely new and inventive approach of managing copies of content and not copies of storage units.

  The duplication / erasure policy aims to optimize the use of storage units while reducing the risk of a blocking situation in which content can not be read by one of the users.

  According to an advantageous embodiment of the invention, the step of managing a number of copies of each of the contents stored on the storage units comprises a step of modification by duplication and / or erasure of the number of copies of each of the contents on one or more storage units so as to maintain the gap between a number of simultaneous read accesses used for the content and / or other content on the storage units in which the content is stored and a number maximum simultaneous read access (nMSA) possible to the contents in the storage units in a predetermined range of values or equal to a predetermined value.

  Advantageously, the step of managing a number of copies of each of the contents stored on the storage units further comprises a step of assigning the maximum number of simultaneous read accesses (nMSA) to each of the contents and the modification by duplication and / or deletion of the number of copies of each of the contents is a function of the duplication / erasure policy which takes into account, for each content, the maximum number of simultaneous read accesses assigned (nMSA) to the content, the number of simultaneous read accesses actually created for the content and the number of simultaneous read accesses used (u) for the content.

  According to a preferred embodiment of the invention, for each of the contents, the duplication / erasure policy is such that: if e <nMSA and * if u <e - n, then a copy quantity of content so that we get: en = u; if u> e m, then we create a quantity of copies of the contents so that we obtain: e m = u and e s nMSA; with nMSA: the maximum number of simultaneous read accesses assigned to the content; n: a margin of erasure of the number of simultaneous read accesses of the content, n0; m: a margin of duplication of the number of simultaneous read accesses of the content, m 0; U: said number of simultaneous read accesses used for the content; e: said number of simultaneous read accesses actually created for the content.

  According to a preferred embodiment of the invention, for each of the contents, the duplication policy comprises the following steps: if e = nMSA, then if u <e - n, then a quantity of copies of the contents of so that we get in = u; * if u e - n, we do not modify the number of copies of the content; with nMSA: the maximum number of simultaneous read accesses assigned to the content; n: a margin of erasure of the number of simultaneous read accesses of the content, na0; m: a margin of duplication of the number of simultaneous read accesses of the content, m has 0; u: the number of simultaneous read accesses used for the content; e: the number of simultaneous read accesses actually created for the content.

  Preferably, the erasure margin n is equal to 1 and the duplication margin m is equal to 1.

  According to a first advantageous implementation of the invention, for each content, the number of simultaneous read accesses actually created for the content includes any simultaneous read accesses actually created that are temporarily unavailable because at least one Storage units that store at least one copy of the content are already used for reading other content.

  According to a second advantageous implementation of the invention, for each content, the number of simultaneous read accesses actually created for the content does not include the possible simultaneous read accesses actually created which are provisionally unavailable because at least one of the storage units that store at least one copy of the content is already used for reading another content.

  According to a first preferred embodiment of the invention, the step of assigning a given content of a maximum number of simultaneous read accesses is triggered by a storage operation of the content.

  According to a second preferred embodiment of the invention, the step of assigning to a given content a maximum number of simultaneous read accesses is triggered at at least one instant independent of the operation execution times of reading or storing content.

  According to a third preferred embodiment of the invention, the step of assigning a given content of a maximum number of simultaneous read accesses is triggered by a read operation of the content.

  Preferably, the step of assigning the maximum number of simultaneous read accesses to each of the contents is performed with user interface means.

  Advantageously, the step of assigning the maximum number of simultaneous read accesses to each of the contents is performed by selection according to at least one criterion, automatically or by a user, of a default value from a set of less a default value.

  According to a first advantageous embodiment of the invention, for each of the contents, the modification step by duplication and / or erasure is triggered by a read operation of the content, the actual reading being performed only after said modifying step.

  According to a second advantageous embodiment of the invention, for each of the contents, the modification step by duplication and / or erasure is triggered by a storage operation of the content.

  According to a second advantageous embodiment of the invention, for each of the contents, the step of modification by duplication and / or erasure is triggered at at least one instant independent of the read operation or read operation times. content storage.

  The invention also relates to a computer program product 30 comprising program code instructions for executing the steps of the content storage management method described above, when the program is run on a computer.

  The invention also relates to an information storage means, possibly totally or partially removable, readable by a computer system comprising instructions for a computer program adapted to implement the content storage management method described above.

  The invention also relates to a content storage management system, each comprising isochronous data, in a communication network to which at least two content storage units are connected and comprising means for managing a number of copies of each. content stored on all storage units, which is a function of a policy of duplication / deletion of copies of content.

  Advantageously, the means for managing a number of copies of each of the contents stored on the storage units comprise means of modifying by duplication and / or erasure of the number of copies of each of the contents on one or more storage units which allow to maintain the gap between a number of simultaneous read accesses used for the content and / or other content on the storage units in which the content is stored and a maximum number of simultaneous read accesses (nMSA) possible to contained in the storage units in a predetermined range of values or equal to a predetermined value.

  Preferably, at least part of the means for managing a number of copies of each of the contents are distributed in at least two nodes of a communication network to which a plurality of storage units are connected.

  The invention also relates to a content storage management device, each comprising isochronous data, in a communication network to which at least two content storage units are connected and comprising means for managing a number of copies of each. content stored on all storage units, which is a function of a policy of duplication / deletion of copies of content.

  Advantageously, the means for managing a number of copies of each of the contents stored on the storage units comprise means of modifying by duplication and / or erasure of the number of copies of each of the contents on one or more storage units which allow to maintain the gap between a number of simultaneous read accesses used for the content and / or other content on the storage units in which the content is stored and a maximum number of simultaneous read accesses (nMSA) possible to contained in the storage units in a predetermined range of values or equal to a predetermined value.

  According to an advantageous characteristic of the invention, the means for managing a number of copies of each of the contents stored on the storage units furthermore comprise means for allocating the maximum number of simultaneous read accesses (nMSA). ) to each of the contents; and the means for modifying by duplication and / or deletion of the number of copies of each of the contents implement the duplication / erasure policy which takes into account, for each content, the maximum number of simultaneous read accesses assigned (nMSA) to the content, the number of simultaneous read accesses actually created for the content and the number of simultaneous read accesses used (u) for the content.

  The invention also relates to a node of a communication network comprising the content storage management device described above.

  5. List of Figures Other features and advantages of the invention will appear more clearly on reading the following description of a preferred embodiment, given as a simple illustrative and nonlimiting example, and the accompanying drawings, among which: FIG 1 shows a diagram of a conventional audio-video network; FIG. 2 illustrates an exemplary implementation of the method of the invention in an audio-video network 20 similar to the network 10 of FIG. 1; FIGS. 3A and 3B illustrate a particular embodiment of the content duplication / deletion policy on which the method according to the invention is based; FIG. 4A shows the diagram of a graphical user interface used to assign the value of a "maximum number of simultaneous access" (or concurrent) reads (nMSA) to a content when this allocation is triggered by an operation storage of this content; FIG. 4B shows the diagram of a general graphical user interface 40 used to assign the value of a "maximum number of simultaneous access" (or concurrent) reads (nMSA) to a content; FIG. 5 presents a first exemplary embodiment of the step of assigning the value of the maximum number of simultaneous read accesses to a content, when this is triggered by a storage operation of this content; FIG. 6 presents a second exemplary embodiment of the step of assigning the value of the maximum number of simultaneous read accesses to a content, when the latter is triggered at at least one instant independent of instants of realization. reading or storing this content; FIG. 7 presents a third exemplary embodiment of the step of assigning the value of the maximum number of simultaneous read accesses to a content, when this is triggered by a reading operation of this content; FIG. 8 shows the diagram of a simultaneous access number storage table, managed by the method of the invention, and comprising different numbers of simultaneous read accesses (maximum, actually created, used) allocated or associated content stored in hard drives; FIG 9 is a flowchart of a recovery algorithm and display, according to the invention, the list of contents of a given hard disk; FIG. 10 is a flowchart of a recovery and display algorithm, according to the invention, of the list of contents of a plurality of hard disks; FIG. 11 illustrates a first exemplary embodiment of the duplication operation of a content, included in the method according to the invention, when this duplication operation is triggered by a reading operation of this content; FIG. 12 illustrates a second exemplary embodiment of the duplication operation of a content, included in the method according to the invention, when this duplication operation is triggered by a storage operation of this content; FIG. 13 illustrates a third exemplary embodiment of the duplication operation of a content, included in the method according to the invention, when this duplication operation is triggered at at least one instant independent of production instants of reading or storing this content; FIG. 14 is a flowchart of the first exemplary embodiment of the operation of duplicating a content illustrated in FIG. 11; FIG. 15 is a flowchart of the second exemplary embodiment of the operation of duplicating a content illustrated in FIG. 12; FIG. 16 is a flowchart of the third exemplary embodiment of the operation of duplicating a content illustrated in FIG. 13; FIG. 17 is a flowchart showing an algorithm for selecting a hard disk for duplicating a content; FIG. 18 is a flowchart of an exemplary embodiment of the operation of erasing a content, included in the method according to the invention, when this erasing operation is triggered at least one instant independent of the instants performing operation of reading or storing this content.

  6. Description of an embodiment of the invention The invention therefore relates to a method for managing a number of copies for each of the contents stored in hard disks of an isochronous data network. This method makes it possible to optimize the use of the hard disks while reducing the risks of occurrence of situations of blocking the read access to a given content, for a user, linked for example to the simultaneous reading of this same content. by other users (at least partial overlap of the reading time slots of different users).

  A copy of a content c is both the copies of the content c and the original of the content c. In addition, the number of copies of a content c includes the original of this content c.

  With reference to FIG. 2, the diagram of an audio-video network 20 similar to the network 10 of FIG. 1 is presented, but implementing, in addition, a preferred embodiment of the content storage management method of FIG. invention. Thus, it is placed in the following in the context of a network 20 of isochronous data type audio-video network (AV). However the skilled person can implement without difficulty the techniques of the invention in any isochronous data network including any type of storage unit.

  For example, it is assumed that the AV content c has been stored on the storage unit D1 which is a hard disk. Prior to this storage, during a step of assigning a value of the maximum number of simultaneous read accesses, the content c has been assigned a maximum access number of 2 by a user by means of an interface graphical user described in the following.

  The maximum simultaneous access number ("Maximum Simultaneous Access Number"), which is assigned to each content, is hereinafter referred to as the maximum number of accesses. This is the maximum number of simultaneous (or concurrent) reads allowed for this content from the network 20. This maximum access number can not exceed the sum of the simultaneous read access numbers on all the hard disks. (For example 4 in the example of the network 20 of FIG. 2, since D1 and D2 can each generate simultaneous read access, and D3 two simultaneous read accesses).

  It is also assumed that later, a first user, from the TV A, triggers a read operation of the content c stored on the hard disk Dl. According to a preferred embodiment of the invention illustrated hereinafter in FIG. 11, at the same time, the content "c" is duplicated. A copy c 'of the content c is thus stored on another hard disk, that referenced D2 for example.

  A short time later, a second user, from the television B, also wants to trigger a read operation of the content c.

  Unlike the case of the conventional network of FIG. 1 (not including the method of the invention), the second user then has the possibility of reading the copy c 'of the content c available on the hard disk D2. A connection is then redirected from the hard disk D2 to the TV B. Anyway, the origin of the contents is transparent from the point of view of users who believe they have access to the content c from the hard disk Dl.

  Figures 3A and 3B. illustrate a particular embodiment of the policy of duplication / deletion of copies of contents on which the method according to the invention is based. This method according to the invention is implemented in the form of a software and / or a plurality of sub-software (comprising a plurality of algorithms described below) which is (are) executed in a or more machines on the network.

  A content c01 whose copies are stored on some of the hard disks D 1 to D 3 of the network 20 is considered.

  In each of FIGS. 3A and 3B, on an axis 34, 35 representing the number of simultaneous read accesses used (denoted by u and hereinafter referred to as the number of accesses used) for the content c01 in the network 20, are placed : - the maximum number of simultaneous read accesses (nMSA) assigned to the content c01; the number of simultaneous read accesses actually created for the content c01 and hereinafter called the number of accesses created; the erasure margin (n) of the number of simultaneous read accesses of the content c01 which may be positive or zero and the duplication margin (m) of the number of simultaneous read accesses of the content c01 which may be positive or none.

  The number of accesses used quantifies, at a given moment, the simultaneous read accesses to a content that are used (or about to be used), that is to say involved in a connection flow in the network. network 20.

  The number of accesses created quantifies, at a given time, the simultaneous read accesses to a content that are actually available in the network 20 (for example, this may be 2 in the case where the original content has been copied to a disk different hard or in the case where the original content was copied to a disc that has at least two simultaneous read accesses).

  Note that, according to a preferred embodiment, the number of simultaneous read accesses used (u) means a number of simultaneous read accesses used or about to be. That is to say, this number takes into account the accesses for which a read request has just been issued by a user and therefore is not really used in reading.

  Figure 3A illustrates the case where e <nMSA. The duplication / erasure policy can then be expressed as follows: if u <e - n, then, in a deletion phase 31, a quantity of copy of the content col is suppressed so that one obtains: en = u ; if u> e m, then in a duplication operation 33, a copy quantity of the content c01 is created so that one obtains: e m = u and esMSA; if u is in the interval [e n, e m], then in a phase 32, no duplication / erasure action is implemented.

  Figure 3B illustrates the case where e = nMSA. The duplication / erasure policy can then be expressed as follows: if u <e - n, then in a phase of deletion, one removes a quantity of copies of the content c01 so that one obtains e n = u; if u z e - n, in a phase 37, the number of copies of the content c01 (e having reached the maximum value allowed, that is to say nMSA), is not modified.

  The duplication margin m of the number of simultaneous read accesses is introduced in order to make it possible to create simultaneous read accesses to the additional content c01 (by creating additional copies of the content c01) in the network 20. This is to satisfy a hypothetical subsequent request from other users and thus reduce the risk of occurrence of situation where the network 20 must deny access to the content c01 to these users.

  The erasure margin n of the number of simultaneous read accesses is introduced in order to make it possible to delete simultaneous read accesses to the content c01 (by deleting copies of the content c01). This, in order to reduce the size of the hard disks D1 to D3 of the network 20.

  In this preferred embodiment, an erase margin equal to the duplication margin is chosen; both are equal to 1. Thus, this allows to always have simultaneous read access, unused, reserved for a user who would like to access the content c01.

  However, the skilled person may choose, depending on the context, any other appropriate value for these margins of duplication and erasure. For example, a value greater than 1 for the erase margin for a network with many users.

  In a first preferred mode of implementation of the invention, for each content of the network 20, the number of accesses created includes any accesses created that are temporarily unavailable on some of the hard drives of the network 20. This unavailability can come from the simultaneous reading of other contents on these same hard disks by other users (at least partial overlap of the reading time slots of different users).

  However, in a second embodiment of the invention, for each content of the network 20, the number of accesses created (e ') takes into account (by temporarily excluding them) any access created that is temporarily unavailable on some of the hard drives of the network 20. Thus the number of accesses created (e ') more truly reflects the availability of content taking into account the availability of hard drives at a given time.

  The following is the case in the case of the first preferred embodiment of the invention. FIG. 4A shows the diagram of a graphical user interface 42 (Graphic User Interface) used to assign the value of a "maximum number of simultaneous access" (or concurrent) reads (nMSA) to a content co2 when it is triggered by a storage operation of this content. This case corresponds to the first preferred embodiment of the step of assigning the maximum access number described below in connection with FIG. 5 according to which the graphical user interface is displayed to a user just before the operation of storage of the content c02.

  By means of this interface, the user is asked to change the value of the "maximum simultaneous access" number to read 43 nMSA (a default value can be proposed) if desired and to press the 0K button. 44 to continue and start the storage operation of the content.

  FIG. 4B shows the diagram of a general graphical user interface 40 used to assign the value of the maximum number of accesses to a content according to a preferred embodiment of the invention.

  According to a preferred exemplary embodiment of the step of assigning the maximum access number described below in relation to FIG. 7, this graphical user interface is displayed to a user just before the operation of reading a content. c02. According to another exemplary embodiment of the invention, it is displayed at a time independent of instants of performing operations for reading or storing this content c02 (described hereinafter with reference to FIG. 6).

  From this interface 40, the user has the possibility of assigning a default value to the maximum number of accesses for all the contents to be stored or even already stored. In this preferred embodiment, the default value is 2, which means that the associated content can be accessed twice simultaneously at a given time (duplication is allowed).

  According to variants of this preferred embodiment, this default value may take any other suitable value. For example, this default value may be 1, this means that the associated content can only be accessed once at a given time (duplication is not allowed).

  Before starting the read operation of the content c02, the user is requested to choose a maximum access number 41 for this content c02 from a list of authorized and predefined values. The user thus enters the value of the maximum access number 41 (default value or any other value) that he wishes to assign to the content c02.

  FIG. 5 shows a first exemplary embodiment of the step 50 of assigning the value of the maximum number of accesses to a content c02 when this is triggered by the operation of storing this content c02 on one of the disks D 1 to D 3 of the network 20 of FIG.

  Before launching the operation of storing content c02 from a user-selected AV source, a maximum default access number of 2 is associated with the content c02 that will be stored. The user is asked to confirm or change this value (as explained in connection with the user interface described in Figure 4A). Either the user confirms this default value, or he chooses, in a step 52, another value from the predefined values authorized in a step 51. In a step 53, this maximum number of accesses is then saved in a dedicated table. called access number storage table which will be described below. The storage operation of the content c02 on a hard disk can then begin.

  It should be noted that the maximum number of accesses by default and that the values of the maximum allowed access numbers (listed in the predefined values) may vary according to the hard disks considered and their properties. Some data of the network 20 of FIG. 2 are recalled: hard disk D1: 1 simultaneous maximum write access, 1 simultaneous access in maximum reading; - Hard disk D2: 1 simultaneous maximum write access, 1 simultaneous access 25 in maximum reading; D3 hard disk: 1 simultaneous maximum write access, 2 simultaneous read accesses.

  The maximum number of read accesses can not exceed 4 (sum of the simultaneous read accesses of the hard disks D1 to D3 of the network 20). In this case, the values of the maximum number of read accesses by default and allowed are between 1 and 4.

  It can be noted that the value of the maximum number of read accesses by default of 2 can be modified by the user. The new default value will be effective for new content only.

  FIG. 6 shows a second exemplary embodiment of the step 60 of assigning the value of the maximum number of accesses to a content c02 when the latter is triggered at at least one instant independent of instants of carrying out operations. for storing or reading this content c02 on one of the hard disks D1 to D3 of the network 20.

  According to a preferred embodiment of this second exemplary embodiment of the invention, this allocation step 60 may be implemented at any time different from the time of performing operations for storing or reading this content.

  We consider the case of this second exemplary embodiment in this preferred embodiment.

  At the beginning of this step, from the assigned content and maximum access number lists displayed in a step 61, for the selected content c02, a user can choose, in a step 62, to change the value of the maximum number of access (from predefined values).

  In a step 63, it is determined whether the maximum access number of the content c02 has changed. In the case where the entered value differs from the previous value, the new value associated with the content c02 is saved, in a step 64, in an access number storage table.

  In the case where the entered value does not differ from the previous value, in a step 65, the procedure is terminated.

  FIG. 7 presents a third exemplary embodiment of the step 70 of assigning the value of the maximum number of accesses to a content c02 when this is triggered by the operation of reading this content c02 on one of the disks D1 to D3 of the network 20 of Figure 2.

  This may be the case, for example, if the user knows at this point that at least one other family member wants to read the same content but at another location in the house with a time lag.

  From the lists of contents and allocated maximum access numbers displayed, in a step 71, the user selects the content c02 that he wishes to read. It then chooses, in a step 72, the value of the maximum number of accesses it wishes to assign to it (for example, it increases the value of the maximum access number). The new value associated with the content c02 is stored, in a step 73, in an access number storage table.

  It may be noted that, for a given content, if nMSA is less than or equal to 2, the step of assigning this nMSA value to the content is preferably triggered by a storage operation of the content (first embodiment of the step assignment shown in Figure 5).

  It may also be noted that, for a given content, if nMSA is greater than 2, the step of assigning this nMSA value to the content is preferably triggered by a content reading operation (third embodiment of step d assignment shown in Figure 7).

  Subsequent to the allocation step (according to the first, second or third embodiment, see the description above of FIGS. 5, 6 or 7 respectively), a step of modification by duplication and / or erasure of the number of copies of this content c02 can be implemented. Three exemplary embodiments of a duplication operation, included in such a modification step, are described below in relation to the pairs of figures (11, 14), (12, 15) and (13, 16).

  FIG. 8 shows the diagram of an access number storage table 80, managed by the method of the invention, and comprising different numbers of simultaneous read accesses (maximum, actually created or used) allocated or associated with contents stored in the hard disks D 1 to D 3 of the network 20 of FIG. 2.

  This table makes it possible to characterize each available content on the network by means of its simultaneous read access numbers. It comprises several columns: a first column 81 comprises the identifiers Id contained in each content that make it possible to uniquely identify them in the network 20 (these identifiers are, for example, names in ASCII characters in this preferred embodiment of the invention); a second column 82 includes the maximum nMSA access numbers of each content (default value or value entered by the user); a third column 83 includes the number of accesses actually created e for each content; a fourth column 84 includes the number of accesses currently used u for each content; a fifth column 85 comprises the hard disk ID IDs of the hard disks D1 to D3 where the original content is stored; a sixth column 86 comprises the list of identifiers Id hard disk drives Dl to D3 where the content has been duplicated (copied). Such an access number storage table 80 is managed by a table management software included in the software according to the invention.

  In a first embodiment according to the invention, only a table management software works in the global network 20 (which means that there is only one access number storage table 80). The table management software is accessed by the graphical user interface 40 which is responsible for displaying the list of contents (as specified above) so as to display updated information with regard to the status of simultaneous read accesses. to contents.

  In a second embodiment, several access number storage tables 80 coexist in the global network 20, each of which is managed by its own table management software. In this second embodiment, it is possible to distinguish two modes of implementation.

  In a first embodiment, each access number storage table 80 only includes the numbers of simultaneous read accesses of the original contents associated with a "local" hard disk ("local" means local at the 1394 bus: the hard disk is connected via an IEEE 1394 link to the network interface adapter 121 to 124). It is necessary to go through the various table management software when looking for a given content. Moreover, two cases can be distinguished: either the graphical user interface communicates with a table management software (for example, the local) which will return the request to all the other table management software, or the graphical user interface asks all table management software to find the simultaneous access numbers for reading the searched content.

  In a second implementation mode, each access number storage table includes all the simultaneous access read numbers of the contents stored on the network 20. A synchronization mechanism between the various table management software is necessary in order to guarantee the integrity of the information (for example, if a maximum number of accesses to a content has been modified in an access number storage table 80, this modification must be taken into account by all the other tables storing the access numbers 80 of the network 20). Then the graphical user interface 40 responsible for displaying the list of contents communicates with only one of the table management software (for example a local software, that is to say a software present on the same node). This second embodiment is safer, for example, in the case where one of the network adapters 121 to 124 is not connected.

  FIG. 9 is a flowchart of a recovery and display algorithm 90, according to the invention, of the list of contents and of their read status (available or not) of a hard disk D1 in the network 20. These steps are implemented by the graphical user interface 40.

  The list of contents is displayed to a user through the graphical user interface 40. This interface can be implemented on each network adapter 121 to 124 independently of the location of the hard disk or drives D1 to D3 in the network 20.

  In a first step 91, the user selects a hard disk D1 by means of the graphical user interface 40. Next, the graphical user interface 40 is responsible for finding the complete list of the original contents and their simultaneous access numbers. in playback assigned or associated with the selected hard disk Dl. It is also possible (optional) to list the contents of the hard disk D l which are not original contents but copies of contents.

  By using the simultaneous read access numbers, for a content c03 of the hard disk D1 in a second step 92, the graphical user interface 40 checks the availability of at least one simultaneous read access of the hard disk including the original of this content c03. If the latter does not have simultaneous read access available, in a third step 93, the graphical user interface 40 selects a hard disk comprising a copy of this content c3. In a fourth step 94, the availability of at least one simultaneous read access of a hard disk comprising a copy of this content c03 is verified.

  If none of the hard drives comprising the content c03 or a copy of the content c03 has available read access, it means that this content c03 has a read status said not available at this time. As a result, this content c03 can not be read and the graphical user interface 40 in a fifth step 95, for example, can use a red font color or any other suitable display means (red diode, transparent mode , ...) to indicate it.

  If one of the hard disks comprising the content c03 or a copy of the content c03 has simultaneous read access available, in a sixth step 96, the graphical user interface 40 means that the content has an available read read status.

  In a seventh step 97, another content is selected in the hard disk D1 and the new set of steps is carried out on this new content, from the second step 92 to the sixth step 96. This step 97 is repeated as well. that the set of steps, from the second step 92 to the sixth step 96, for each content of the hard disk Dl.

  In an eighth step 98, the graphical user interface 40 displays the list of contents of the hard disk Dl and their read status.

  In a ninth step 99, the user selects a content available for reading and requests its reading. Then, in a tenth step 991, the hard disk on which the content or a copy of the content is available for reading is used to establish a connection to implement the reading of this content.

  Since time has elapsed between when the user has selected the hard disk D1 in the first step 91 and the moment when the user starts the read operation in the tenth step 991, the graphical user interface 40 must have a status display of the updated content. This is why the graphical user interface 40 must listen for any notification from the table management software or software about any changes.

  FIG. 10 is a diagram showing the steps of the recovery and display method 100, according to the invention, of the list of contents and of their read status (available or not) of a plurality of hard disks D1, D2 and D3 in the network 20. These steps are implemented by the graphical user interface 40.

  In this method, and unlike the display method 90, all visible contents on the entire network 20 (from the different hard disks D1 to D3) are displayed to the user.

  The steps of this method 100 are identical to those of the display method 90 except for the presence of an additional step 101 which is implemented between the seventh step 97 and the eighth step 98 of the method 90. to switch to another hard disk once all steps have been implemented, from the second step 92 to the seventh step 97, for a first hard drive. This step is repeated so as to be able to implement all the steps, from the second step 92 to the seventh step 97, for each hard disk D 1 to D 3 of the network 20.

  FIG. 11 illustrates a first exemplary embodiment of the operation of duplicating a content CO stored on the hard disk D2, included in the method according to the invention, when this duplication operation is triggered by a read operation of this content. Of course, in a particular embodiment, the duplication operation is implemented just before the actual reading operation begins. For the sake of clarity, only the television set A is shown on the network of this FIG. 11 as well as in FIGS. 12 and 13 which will be described hereinafter.

  It may be noted that in this Figure 11, as well as in Figures 12 and 13 which will be described below, only a table management software (which is designated by AM) is implemented. This table management software runs on the network adapter 121 connected via an IEEE 1394 link to the television A. The value of the maximum number of access to the content CO has been chosen equal to 2 (or the default value is 2).

  After having detected a request for reading by a user and before starting the actual reading operation, from the graphical user interface 40, the software according to the invention implements the duplication algorithm which will be described in FIG. 14 for CO content. In this case, we have the creation of a copy and CO on the hard disk D3.

  As a result, the content CO (in the hard disk D2) is duplicated once (copy cl in the hard disk D3). Thus, it can be accessed twice simultaneously during playback: a first simultaneous read access in the hard disk D2 (1st output) and a second simultaneous read access in the hard disk D3 (2nd output).

  FIG. 12 illustrates a second exemplary embodiment of the operation of duplicating a content CO stored on the hard disk D2, included in the method according to the invention, when this duplication operation is triggered by a storage operation of this content. Of course, in a particular embodiment, the duplication operation is implemented just before the storage operation itself begins.

  The value of the maximum CO content access number has been chosen equal to 3 (or its default value is 3).

  After having detected a storage request by a user and before starting the actual storage operation, from the graphical user interface 40, the software according to the invention implements the duplication algorithm which will be described in FIG. for CO content. In this case, we have the creation of two copies and c2 of the content CO on two different hard disks respectively Dl and D3.

  As a result,: the content CO (in the hard disk D2) is duplicated twice (copy C1 in the hard disk D3 and copy c2 in the hard disk D1). Thus, it can be accessed 3 times simultaneously: a first simultaneous access to the output in the hard disk D2 (the output), a second similar access read in the hard disk D1 (2nd output) and a third simultaneous read access to the hard disk D3 (3rd output).

  It may be noted that, in this case, the value of the maximum access number could have been chosen equal to 4, with the two duplications on the two hard disks D1 and D3. Indeed, one could have 4 simultaneous read accesses to the content CO since the hard disk D3 can provide up to two simultaneous read accesses.

  FIG. 13 illustrates a third exemplary embodiment of the operation of duplicating a content c0 stored on the hard disk D2, included in the method according to the invention, when this duplication operation is triggered at least at an independent instant of time. instants of performing operations for storing or reading this CO content.

  According to a preferred embodiment of this third exemplary embodiment of the invention, this duplication operation is implemented during a background processing operation. This background operation operation is implemented on a regular basis every day or, according to a variant of this embodiment, during periods of low network use, for example between 2h and 5h.

  We consider the case of this third embodiment in this preferred embodiment.

  The value of the maximum number of accesses to the content c0 has been chosen equal to 3 (or the default value is 3).

  Regularly (and especially during periods of calm, for example between 2 hours and 5 hours as specified above), and in agreement with the status of hard disks (access input and output, free space available in hard disks), the software according to the invention implements the background processing operation of the contents stored on the hard disks D1 to D3 of the network 20.

  During this background processing, the software according to the invention implements the duplication algorithm which will be described in FIG. 16 for the content CO and in this case, two duplications result on the two hard drives D1 and D3 respectively.

  Thus, the content CO (in the hard disk D2) has been duplicated twice (copy c 1 in the hard disk D3 1'ee copy and copy c2 in the hard disk Dl 2nd copy). Thus, it can be accessed 3 times simultaneously in reading.

  It can once again be noted that, in this case, the value of the maximum access number could have been chosen equal to 4, with the two duplications on the two hard disks D1 and D3. Indeed, one could have 4 simultaneous read accesses to the content CO since the hard disk D3 can provide up to two simultaneous read accesses.

  It may be noted that, for a given content, if nMSA is less than or equal to 2, the step of duplicating the content is preferably triggered by a content storage operation (second embodiment of the duplication operation of a content shown in Figure 12).

  It may also be noted that, for a given content, if nMSA is greater than 2, the step of assigning this nMSA value to the content is preferably triggered by a content read operation (first embodiment of the operation of duplication illustrated in Figure 11).

  FIG. 14 is a flowchart 140 of the first exemplary embodiment of the duplication operation, of a content CO stored on a hard disk D2, illustrated by FIG. 11.

  It is recalled that this duplication operation is implemented by the software according to the invention after detecting a request to read this content c0 by a user and before starting the read operation itself.

  We denote nMSA, the maximum number of access to the content CO.

  In a first step 141, the number of accesses used u for the content CO is incremented by one unit because of the transmission of a request to read the content CO by the user.

  In a second step 142, it is checked whether the number of accesses used u for the content CO satisfies the relation: u e-m.

  In the case where u e - m, in a third step 143, one checks whether e <nMSA.

  If e <nMSA, in a fourth step 144, the duplication operation itself is implemented. In addition to the installation of the connection between the hard disk D2 including the content CO and the destination: the TV A, a second connection (called overlaid English or recovery in French) is implemented between the hard drive D2 and a another hard disk D3 chosen as hard disk duplication (on which will be stored the copy of the content CO).

  If e = nMSA, in a fifth step 145, no duplication operation per se is allowed, the maximum number of accesses to the content CO has been reached. In the case where another read request is implemented consecutively, simultaneous read access to the content CO will not be allowed until a hard disk comprising the original of the content CO or a hard disk comprising a copy of content CO presents again simultaneous read access available.

  In the case where u <e-m, there remains at least one simultaneous read access to the content CO available in the hard disks D1 to D3 of the network, in a sixth step 146, there is no need to launch the duplication operation itself.

  Finally, the content CO is read in a seventh step 147.

  FIG. 15 is a flowchart 150 of the second exemplary embodiment of the duplication operation, of a content CO stored on a hard disk D2, illustrated in FIG. 12.

  It is recalled that this duplication operation is implemented by the software according to the invention after detecting a request for storing this CO content by a user and before starting the actual storage operation.

  We denote nMSA, the maximum number of access to the content CO.

  In a very first step 150a, the number of simultaneous read accesses actually created for the content c0 is incremented by one and updated at the MSA table; this new value of e aims at taking into account the result of the storage operation (step 155) ,.

  Then, in a step 151, it is checked whether the number of accesses used u for the content CO satisfies the relation: u e-m.

  In the case where u e-m (it can be noted that when the original content CO is recorded for the first time, u = e = 0), in a second step 152, it is checked whether e <nMSA.

  If e <nMSA, in a third step 153, the duplication operation itself is implemented (it can be noted that when the original of the content CO is recorded for the first time, the duplication operation itself content c0 is implemented anyway according to the preferred embodiment for which the erasure margin is 1). In addition to implementing the connection between the source of the content CO and the hard disk D2, a second connection (called overlaid in English or recovery in French) is implemented between the source of the content CO and another hard disk D3 chosen as a duplicate hard disk (on which will be stored the copy of the CO content).

  If e = nMSA, in a fourth step 154, no duplication operation itself is allowed, the maximum number of accesses to the content CO has been reached.

  In the case where u <e-m, there remains at least simultaneous read access to the content CO available in the hard disks D1 to D3 of the network (this may be the case when the content CO has already been stored on the network to a previous moment), in the fourth step 154, there is no need to start the duplication operation itself.

  Finally, the original CO content is stored in a fifth step 155. FIG. 16 is a flowchart 160 of the third exemplary embodiment of the duplication operation, of a content CO stored on a hard disk D2, illustrated by FIG. .

  We denote nMSA, the maximum number of access to the content CO.

  In a first step 161, a background processing operation is initiated by the software according to the invention. It is recalled that this operation is implemented on a regular basis or during periods of low network activity.

  It is during this background processing operation that the steps of the algorithm of the duplication operation according to this exemplary embodiment take place.

  In a second step 162, it is checked whether the number of accesses used u for the content CO satisfies the relation: u e-m.

  In the case where u e - m, in a third step 163, it is checked whether e <nMSA.

  If e <nMSA, in a fourth step 164, the duplication operation itself is implemented. A connection is installed between the hard disk D2 including the content CO and another hard disk D3 chooses as duplication hard disk (on which will be stored the copy of the content CO).

  If e = nMSA, in a fifth step 165, no duplication operation itself is allowed, the maximum number of accesses to the content CO has been reached.

  In the case where u <e-m, there remains at least one simultaneous read access to the content CO available in the hard disks D1 to D3 of the network, in the fifth step 165, there is no need to launch the duplication operation itself.

  Fig. 17 is a flowchart 170 showing a hard drive selection algorithm for duplicating a CO content.

  This algorithm 170 is implemented prior to the actual duplication operation of the content CO.

  In a step 171, the information of the table MSA concerning the content CO is used in particular to select a hard disk (for example D2), among the hard disks of the network 20 having at least one simultaneous read access available and not including still the content CO. This hard disk D2 is called hard disk duplication and will receive the copy of the content CO. It is recalled that the hard drives that include the content CO are registered in the lists Id hard disk (original content) (column 85) or Id hard drives (copies) (column 86) of the access number storage table or tables 80 of the network 20 as shown in Figure 8.

  This hard disk information D2 is then stored in the access number storage table or tables 80 of the network 20 at their hard disk ID (copies) columns 86. It is the same any value (for example e) having has been modified.

  In a second step 172, a connection dedicated to this duplication operation itself is installed from the source of the content CO (either the source AV or a hard disk comprising a copy or the original content CO) to the hard disk of duplication D2.

  In a third step 173, the duplication operation itself is implemented and the number of copies actually created of the content CO is incremented by one unit consecutively.

  FIG. 18 is a flowchart 180 of an exemplary embodiment of the operation of erasing a content, included in the method according to the invention, when this erasing operation is triggered at least one instant independent of the instants performing operation of reading or storing this content.

  In a first step 181, a background processing operation is initiated by the software according to the invention. It is recalled that this operation is implemented on a regular basis or during periods of low network activity.

  In a second step 182, it is checked whether the number of accesses used u for the content CO is such that u <e-n.

  In the positive case in a step 183, it is verified that the actual number e of content CO is strictly greater than 1 (indeed at least one version, original or copy, of the content CO must be kept). If it is the case the erase operation itself is implemented in step 184. Otherwise the process ends (step 185). The operation is re-iterated as necessary.

  In step 184 a hard disk containing the content CO is selected (using the information stored in the MSA table), then the content CO is deleted from the previously selected hard disk, and finally the MSA table is updated.

  In the case where the test of step 182 is negative, there is no need to start the erase operation itself.

  The storage management method according to the invention is implemented in the form of a software and / or a plurality of sub-software (comprising a plurality of algorithms described above) which is (are) executed in one or more nodes of the network. The nodes represent the network adapters 121, 122, 123 and 124 of FIG.

  To perform a deletion of a content, a node implementing the invention uses the information contained in the storage table to determine the identifier of the content to be erased and the identifier of the disk having this content. This node then transmits an erase request containing this information to the controller of the disk concerned. The address of the disk controller can be obtained from the disk identifier.

  To make a copy of a content, a node implementing the invention uses the information contained in the storage table to determine the identifier of the content to be copied, the identifier of the source disk having this content as well as that of the destination disk in which copy will be made.

  This node then transmits requests to establish a connection between the controllers of the source disk and the destination disk as well as the initialization of the data transfer. The node must also send queries to break the connection after the copy has been made to free the network resources.

  FIG. 19 represents a block diagram of a node in which the storage management method according to the invention can be implemented.

  The node comprises a microcontroller 411 which will ensure the transfer of the information from the different interfaces to the memory 412 or directly to the FIFO type memories (First In First Out in English) of the output interfaces (401, 402, 403 , 404, 405).

  The microcontroller 411 is also responsible, at power up of the node, to load the program implementing the invention stored in the rewritable permanent memory (flash memory) 413 in the RAM 412 in order to execute the associated code instructions to this program. The memory 413 may also contain the storage table which is loaded into the RAM for updating or reading.

  The node comprises a set of physical interfaces according to different communication standards with associated circuits or link programs. These interfaces are for example a referenced interface 403 Ethernet type for the exchange of data with terminals such as computers. An interface referenced 404 for the exchange of isochronous and asynchronous data on a bus with terminals compatible with the IEEE 1394 standard. An interface referenced 402 for sending or receiving infrared signals for the exchange of commands. An interface 410 for exchanging data with the switch 11.

  The node also interconnect on analog devices. To do this it has an analog input module 406 for analog / digital conversion of input AV signals and a 407 coding module of this signal into an encoded AV signal (MPEG2, DV, ...). At this interface can be connected an analog audio / video source such as a multimedia decoder with analog output for example. For the output AV signals, a module referenced 409 enables the decoding of an encoded AV signal before it is converted into an analog signal in the output module 408. At this interface can be connected audio / video equipment such as for example a television set or an analog display screen. The reception and transmission of coded AV signals is managed by the AV interface referenced 405.

  The referenced module 401 contains a character generator that allows the insertion of information by superposition to the AV signal output (On Screen Display in English terminology). This information is intended for the user and allows him, for example, to receive information messages on the display screen. The association of the information received by this interface and commands sent by the user through the infrared interface 402 allows the navigation in a menu, the control of an action, a setting or a selection, or the control of equipment network.

  The user can transmit his commands to the node using a remote control. A remote control is associated with each node of the backbone. This remote control can be dedicated to the node or multifunction also allowing the control of one or more other terminals connected to the node as a TV.

Claims (25)

  A method for managing the storage of contents, each comprising isochronous data, in a communication network (20) to which at least two content storage units are connected, characterized in that it comprises a step of managing a number of copies of each of said contents stored on all the storage units, which is a function of a policy of duplication / erasure of said copies of contents.   2. Method according to claim 1, characterized in that said step of managing a number of copies of each of the contents stored on the storage units comprises a step of modification by duplication and / or erasure of said number of copies of each of the contained on one or more storage units so as to maintain the difference between a number of simultaneous read accesses used for said content and / or other content on the storage units in which said content is stored and a maximum number of possible simultaneous read access (nMSA) to said content in the storage units in a predetermined range of values or equal to a predetermined value.   3. Method according to claim 2, characterized in that said step of managing a number of copies of each of the contents stored on the storage units further comprises a step of assigning said maximum number of simultaneous accesses to reading (nMSA) to each of the contents; and in that said modification by duplication and / or erasure of said number of copies of each of the contents is a function of said duplication / erasure policy which takes into account, for each content, said maximum number of simultaneous read accesses assigned (nMSA ) to said content, the number of simultaneous read accesses actually created for said content and the number of simultaneous read accesses used (u) for said content.   4. Method according to claim 3, characterized in that for each of the contents, said duplication / erasure policy is such that: if e <nMSA and * if u <e - n, then one suppresses (31) a quantity of copies of said content so that one obtains: en = u; r * if u> e m, then we create (33) a quantity of copies of this content so that we obtain: e m = u and e s nMSA; with nMSA: said maximum number of simultaneous read accesses assigned to said content; n: a margin of erasure of the number of simultaneous read accesses of said content, n has 0; m: a margin of duplication of the number of simultaneous read accesses of said content, m 0; u: said number of simultaneous read accesses used for said content; e: said number of simultaneous read accesses actually created for said content.   5. Method according to any one of claims 3 or 4, characterized in that for each of the contents, said duplication policy comprises the following steps: -si = nMSA, * if u <e - n, then, we delete a quantity of copies of said content so that one obtains in = u; * if u a e - n, we do not modify the number of copies of this content; With nMSA: said maximum number of simultaneous read accesses assigned to said content; n: a margin of erasure of the number of simultaneous read accesses of said content, n z 0; m: a margin of duplication of the number of simultaneous read accesses of said content, m z 0; u: said number of simultaneous read accesses used for said content; e: said number of simultaneous read accesses actually created for said content.   6. Method according to any one of claims 4 and 5, characterized in that said erasure margin n is equal to 1 and said duplication margin m is equal to 1.   7. Method according to any one of claims 3 to 6, characterized in that, for each content, the number of simultaneous read accesses actually created for said content includes any simultaneous read accesses actually created which are temporarily unavailable. because at least one of the storage units that store at least one copy of said content is already used for reading another content.   8. Method according to any one of claims 3 to 6, characterized in that, for each content, the number of simultaneous read accesses actually created for said content does not include any simultaneous read accesses actually created which are provisionally unavailable because at least one of the storage units that store at least one copy of said content is already used for reading another content.   9. Method according to any one of claims 3 to 8, characterized in that said step of assigning (50) a given content of a maximum number of simultaneous read accesses is triggered by a storage operation of said content .   10. Method according to any one of claims 3 to 8, characterized in that said step of assigning (60) to a given content of a maximum number of simultaneous read accesses is triggered at least one independent time d instants of performing operation of reading or storing said content.   11. Method according to any one of claims 3 to 8, characterized in that said step of assigning (70) a given content of a maximum number of simultaneous read accesses is triggered by a read operation of said content .   12. Method according to any one of claims 3 to 11, characterized in that the assigning step (50; 60; 70) to the maximum number of simultaneous read accesses to each of the contents is performed with means user interface (41; 42). 13. Method according to any one of claims 3 to 12, characterized in that the step of assigning the maximum number of simultaneous read access to each of the contents is performed by selection according to at least one determined criterion, automatically or by a user, a default value from a set of at least one default value.   14. Method according to any one of claims 2 to 13, characterized in that, for each of the contents, the modification step by duplication (140) and / or erasure is triggered by a read operation of said content, the reading itself only after said modifying step.   15. Method according to any one of claims 2 to 13, characterized in that, for each of the contents, the step of modification by duplication (150) and / or erasure is triggered by a storage operation of said content.   16. Method according to any one of claims 2 to 13, characterized in that, for each of the contents, the modification step by duplication (160) and / or erasure is triggered at least one instant independent of instants of performing operation of reading or storing said content.   17. Computer program product, characterized in that it comprises program code instructions for executing the steps of the content storage management method according to any one of claims 1 to 16, when said program is run on a computer.   18. An information storage medium, possibly totally or partially removable, readable by a computer system, characterized in that it comprises instructions for a computer program adapted to implement the content storage management method according to the present invention. one of the Claims 1 to 16.   19. Content storage management system, each comprising isochronous data, in a communication network to which at least two content storage units are connected, characterized in that it comprises means for managing a number of copies. each of said contents stored on all the storage units, which is a function of a policy of duplication / erasure of said copies of contents.   20. The system as claimed in claim 19, characterized in that said means for managing a number of copies of each of said contents stored on said storage units comprise means of modification by duplication and / or erasure of said number of copies of each of said storage units. content on one or more storage units which maintain the gap between a number of simultaneous read accesses used for said content and / or other content on the storage units in which said content is stored and a maximum number of possible simultaneous read access (nMSA) to said content in the storage units in a predetermined range of values or equal to a predetermined value.   21. Management system according to any one of claims 19 and 20 characterized in that at least a portion of said means for managing a copy number of each of said contents are distributed in at least two nodes of a communication network. to which a plurality of storage units are connected.   22. A content storage management device, each comprising isochronous data, in a communication network to which at least two content storage units are connected, characterized in that it comprises means for managing a number of copies. each of said contents stored on all the storage units, which is a function of a policy of duplication / erasure of said copies of contents.   Device according to claim 22, characterized in that said means for managing a number of copies of each of the contents stored on the storage units comprise means of modification by duplication and / or erasure of said number of copies of each of the content on one or more storage units which maintain the gap between a number of simultaneous read accesses used for said content and / or other content on the storage units in which said content is stored and a maximum number of possible simultaneous read access (nMSA) to said content in the storage units in a predetermined range of values or equal to a predetermined value.   24. Device according to claim 23, characterized in that said means for managing a number of copies of each of the contents stored on the storage units furthermore comprise means for allocating said maximum number of simultaneous accesses in reading (nMSA) to each of the contents; and in that said means for modifying by duplication and / or erasure of said number of copies of each of the contents implement said duplication / erasure policy which takes into account, for each content, said maximum number of simultaneous read accesses assigned (nMSA) to said content, the number of simultaneous read accesses actually created for said content and the number of simultaneous read accesses used (u) for said content.   25. Node of a communication network characterized in that it comprises a content storage management device according to any one of claims 22 to 24.