FR2468163A1 - VIRTUAL STORAGE DEVICE AND METHOD - Google Patents

Abstract

A device and method for managing a data memory, for use in conjunction with a "main" digital computer. The device responds to requests from the main computer 10 for storing and retrieving information with the same structure as in a set of conventional tape drives. However, the data is actually stored or retrieved as fragments of information in or from a plurality of disk storage elements 22, so that the data management device functionally simulates a tape drive. and accepts and produces data in sequential (tape) form when in fact it stores the data in available spaces in disk drives.

Description

The present invention relates to memorization or storage means

digital data and,

more particularly, a device and a method suitable for

Formulated for the management and allocation of data in a disk storage device. One of the main considerations, of which he

must be taken into account when designing and operating

operation of a digital data processing device

ques, is the need to provide suitable means for storing information received from the central unit

(CPU) of the computer and to provide relevant information

owned by the CPU when needed.

It is generally accepted that tape memories

magnetic and disk memories have

different and specific functional characteristics.

Accordingly, each of these types of information media

tion is particularly suitable for certain types of application.

cations but not to others. In particular, the fi

Sequentially organized and also sequentially accessed data les are the most compatible with tape drive technology since the information is necessarily written and read from the tape sequentially. In contrast, disk storage devices generally provide the ability to write to and read information from virtually any part of the disk almost instantly. As a result, multiple data sets, all stored on the same disk,

can be active simultaneously, which is not practical.

tickable with tape. Consequently, we prefer-

would still use -2- disk memory devices if it were not that a disk memory is

much more expensive than tape.

As a result, while data organized in sequential can be easily written and read continuously on a tape, writing or obtaining data that is not organized in sequential is often a problem. If a data is located on a

part remote from the tape, it must be wound up

rolled out or rolled out to the point at which the data is located. A second, much more serious disadvantage of tape memory is the fact that for most large scale applications the number of tape reels required to store information is much greater, sometimes hundreds of times greater. , that the number of tape drives available

to read or write to tapes. In fact, by name

Many large-scale data processing operations require the use of thousands of reels of tape. Typically, about 90% of all tapes contain only one set of data (for example, a customer list or a data file).

payslips), given that in general

physical properties of the tape make it impractical to read or write to two or more data sets at a time, which is

very often desirable. It is therefore clear that a

tape memory is very inefficient, because it cannot

only by pure coincidence that the length of an en-

data appears determined to be approximately equal to the available memory area. In fact, studies show that normally only around 1%

of the tape is actually used.

It is obvious that no user can have a tape unwinder for each reel of tape; as a result, individual coils are

continuously taken from their storage location

ment, mounted with a view to their use, then

tees and returned to their store. These operations

take a long time and are not very efficient.

these since they involve the intervention of a

human operator.

Efforts have been made to fill this gap in the information medium constituted by the magnetic tape, for example by providing a large number of

small tape cartridges and an automatic mechanism

tick for quickly removing cartridges from a storage bin and quickly placing them on a tape dispenser. Mounting devices

automatic systems have also been created for use.

edged with classic tape. However, there is no

To date, no absolutely effective process allows

so much to immediately put large amounts of

tape available to tape unwinders.

At first glance, disk storage devices would seem apt to fill the gaps in

the band. You can quickly access practical-

ment any part of any disc, from

so that a disc device does not need to be

plore all the data recorded on the disks sequentially. As a consequence by responding to address codes, a disk drive can access

to a given block of data almost instantly.

Multiple data sets can therefore be stored on a single disk and be processed concurrently. However, the cost of disk units

is relatively high and, in addition, the dis-

that of the prior art do not use much

efficiently all possible storage area.

Studies have shown that at any given moment

born any, in a disc device, 75% in-

-4- only about the possible storage space is

in fact available for data storage purposes.

born. The "maneuver zone" or memory space to-

tal used to enable reading / writing activity

necessary to update and save the

data is therefore approximately 20% to 25%.

In addition, for most applications, only about 2/3 or 45% of the available data space is actually used for storing data.

data, due to the space required by the

Commonly used addressing tifs. Consequently, the

total duty cycle of most devices

Prior art disc devices are only

by about 50% or less. Consequently, the provisions

disc tives, although they offer higher speeds

These attractive data access and high data extraction are relatively inefficient to the point

cost and hence can be costly,

derived from the point of view of effective memory space

ment used. On the other hand, in a tape device,

only one address is required per data set

born, which significantly increases the efficiency

of memory.

We can therefore see that it would be extremely advanced.

necessary to produce a device offering both the efficiency of the information medium consisting of

the tape from the point of view of memory space and the

fast access feature of a disk memory.

Furthermore, as a desirable feature, such a memory device would require no modification of the rest of the computing installation concerned; in others

terms, it would "show up" to the exact computer-

in the same way as a tape memory or a

prior art disk memory.

In view of the above, the object of the invention -5 - is to create:

- an improved storage device for computers

nator, digital calculator, or the like; - a device and a method for storing sequentially arranged data and accessing

to these data more quickly than in the

prior art storage materials; a storage device responding to commands from the main device in the manner of a tape drive but making use of the rapid access capacity of the disk units; - a data memory management device which

accepts and delivers data in sequential form

tielle but which records and retrieves information on disk drives in the form of optimal fragments. In one of the aspects of the invention, the objects enumerated above are achieved by means of a "virtual storage device" comprising a main junction stage capable, in response to commands from a main computer, of receive and

transmit information with a se-

band type quential and a first data buffer

born in said main junction to temporarily store data received from or directed to the main computer. A plurality of disk drives are also provided together with a disk junction and with an associated second data buffer which temporarily stores data directed to or received from the disk drives. The trunk stages are coupled together and are also coupled in common with a large central memory which receives and queues information passing from one trunk to another. Finally, a main control processor is coupled with the junction units and with the main memory and directs the operation of the apparatus such that the main junction stages respond to the main computer in the same way as. would do a tape device, while the disk junction stages read and write data to disk memories randomly

or direct, depending on the current memory space -

currently available.

The invention will be better understood on reading

of the following detailed description and examination of the

attached drawings which represent, by way of example

non-limiting, a preferred embodiment.

In these drawings: FIG. 1 represents the general organization of a virtual storage device constructed according to the invention;

Fig. 2 is a simplified diagram represented

both the circulation of control signals and information

mation 'in the device of FIG. 1, and Figs. 3 and 4 indicate the circulation of

signals of order and information in situations

terms of "read" and "write" respectively.

Fig. 1 represents in simplified form

based on the basic architecture of the storage device

virtual tion according to the invention when the latter is coupled with a main computer 100 The invention

constitutes a means of ordering one or more

These extremely fast and accessible disk memory units to make them accept data and make them respond in exactly the same way as a tape drive while making much better use of available memory,

so that they in fact provide a storage capacity

greatly enlarged kage and a much faster response time than tape or disks. Main computer 10 can be of any suitable type,

although it can be expected that the economic operation

The logic of the present invention will require its use with a large CPU main computer, such as the IBM 360 or 370 computers and the IBM Model 3031, 3032 and 5033 processor complexes.

virtual storage device according to the invention

tion can also be used with a plurality

main computers. The memory device

tion comprises a series of main junction stages 12a to 12n, the number of these junction stages being a function of the quantity of data to be transferred. Being

since the main junction floors are identical

ticks, the actual number of these stages to be used is irrelevant for the purposes here. The main trunk stages are coupled to the main computer 10 by means of conventional channels 14 and they receive and transmit information from the computer 10, or to it with the ordinary sequential configuration associated with the unwinders. bandaged.

One or more disconnect junction stages

ques 16a to 16n are provided and are coupled with all main junction stages by means of a bus

common information 18. In this way,

formation can be transferred between a ring stage

principal tion given any and any

disc junction stage.

The disc junction stages are cut

each with one of a series of respective disk memories 20a to 20n. As described in more detail below, each disk junction stage includes a memory junction, a data buffer

and a disc junction, together with a disc junction

-8- local microprocessor control positive intended for

order the various elements of the junction stage.

To the main bus 18 is also connected a central memory 22. The memory 22 forms a "shelter" or "cache" for information transferred from the floors.

from the main junction to the dis-

ques and can further serve as memory to the control processor 24 also coupled with the main bus

18. The control processor 24, which constitutes the uni-

central tee or CPU of the vir-

current, is coupled with each of the main junction and disk stages 12 and 16, respectively, and directs the operation of these stages in such a way that information can be received, queued

waiting, organized and stored in the appropriate way

nable. The control processor 24 furthermore gives

instructions to the various main junction floors

pale 12 to make them answer the main computer

pal 10 in a way that simulates a tape drive.

We will now refer to FIG. 2, on which is shown in more detail the

structure of examples of elements of the device. The pro-

cessor 24 is coupled directly with the main junction stage 12 and, in particular, with a

internal junction 26, which simply facilitates the trans-

signal flow between the control processor 24 and

a microprocessor 28, which forms the control device

order from the main junction floor. The main junction stage also includes a data buffer 30, a main junction 32, which makes the

data buffer compatible with the main computer

pal 10 and a memory junction 34, through

diary of which the data buffer communicates

with the data bus 18.

The function of the main junction stage -9-

12 is to simulate for the main computer an available

tape drive device, that is to say to convert the orders of the main computer 10 intended for tape drives into orders for the virtual storage device according to the invention and to transmit to the main computer 10 data in the form they would present if they were

transmitted by a tape drive. More particularly

Rather, the main junction stage 12 accepts signals from a main computer 10, which signals are of the type used to operate the unwinders.

of tape. Such signals are obtained by coupling the e-

main junction floor with multi-track

block or byte, or select, plexing of main computer 10. Note that these signals include operator commands such as mount tape "and" unmount tape "t as well as machine commands such as" read. "," write "and" space ". The main junction stage responds to these two types of signals as if it were an operator

and a tape drive by acknowledging receipt of the

general, responding that an imaginary (virtual) tape reel has been "edited", and so on. The data buffer 30 of each stage of

main junction accepts data from the computer

Primary 10 in sequential form, typically nine bits in parallel, in exactly the same way that this data would be retransmitted to a tape device for writing to tape. The buffer 30, together with the main junction 32, during a write operation,

"deequentializes" the information, that is to say the

morise in parallel areas containing the individual bits until eight full bytes

are available. Typically 72 bits are trans-

*

- -10-

at the same time, which reduces the transmission time. In this way, it is possible to obtain a compression of up to 90% of the time required to transmit the data on the bus 18. When data must be exchanged between the buffer 30 and bus 18,

data cross memory junction 34, here in-

core in eight parallel or simultaneous bytes, so that extremely fast data exchange can

take place. The size of said tampon can vary widely-

according to the requirements of the device but, in a preferred embodiment, it is large enough (64,000 bytes) that this buffer can hold a complete record, which speeds up

the time-sharing operation of the bus 18.

Finally, the data received from the computer

main tenor 10 are written on magnetic discs.

ticks mounted on one or more disk drives a through 20n. The disk junction stage 16 couples the data bus 18 with a disk drive 20 (not

shown) and consists of a control device

local control 36 with microprocessor, which operates

the various elements of this junction stage conforming to

ment to the instructions of the control processor 24.

As in the case of the main junction stages

blade 12, by means of the disk junction stages 16, instructions from the control processor are transmitted, via a junction 38, to the local control device 36. The latter then responds by causing data to be transferred by a buffer

data 20, a junction of disks 42 and a junction

memory 44 to the disk drive or from

of it.

In particular, memory junction 44 serves to receive eight bytes of data from bus 18 and to "sequence" the data so that it is installed in buffer 40 as a single bit stream. Arrangement and queuing

waiting for data in the buffer are ensured.

res by the local controller 36, as well as the operation of the disc junction 42, which

passes data from buffer 40 to the dis-

ques at the appropriate times. In addition, the floors of

disc junction are used to search and record

tracing the data locations on the various disks

associated disk drive, so that the information

tion can be found at the right time.

Between the instant at which a datum is in a main junction stage 12 and the instant

at which it is received in a disconnect junction stage.

ques 16, this data is stored in a central memory.

In general 22, the fast main memory 22 therefore acts as a "bank", "cache" or "shelter", which holds data until one of the disk drives 20 is ready to accept it. When this occurs, the disk junction 42 associated with the disk unit 20

signals its availability to the control processor 24.

The control processor 24 then gives the memory

central "shelter" 22 the instruction to unload the data

born in the disc junction stage 16 by the inter-

mediary of the bus 18.

Similarly, when the computer

main 10 data search, the identity of the data

wanted is transferred through

the main junction stage 12 to the control processor

command 24, which then determines whether the requested data

have been previously transferred to central memory

trale. If not, the control processor 24

in turn applies a "transmit" signal to the

disc junction stage 16 and the control device

local command 36 thereof causes the extraction of -12- data in the associated buffer 40, their transmission through the associated memory junction 44 up to

the data bus 18 and from there to the central memory

trale 22.

At the same time, the local control device

28 of the main junction floor 12 available de-

locks the associated memory junction 34, so

that the newly read data is received from the

central memory 22 and transmitted in the data buffer

born 30 from the main junction floor. Furthermore, if this has happened, the data is immediately extracted from the buffer 30, "sequenced" by the main junction module 32 and transmitted to the computer.

main 10.

In an alternate embodiment, the main buffers 30 and the disk buffers 40 may be omitted, their functions then being

provided by the main memory 22.

In this way, segments of data that have been scattered among a number of disk drives can be compiled, queued

then reassembled automatically in sequential form.

As a result, the information reaching the main computer 10 from the various disk drives 20 appears in sequential form, just as

if it was read on a tape.

As previously described, the memory

rapid plant constitutes a "shelter" in which data

borns can be selected and queued in

view of their subsequent reassembly in the se-

quential before they are sent to the main computer.

cipal. As those skilled in the art will readily understand in light of the teachings of the present invention, the various elements of the virtual storage device according to the invention can be used.

assembled from elements available in the

merce and can be coupled together in any convenient way. For example, although the various elements of the disc junction stage 16 are

represented as being all arranged in a single em-

placement away from the control processor 24, in fact these elements may be arranged in different locations and may be coupled by means of suitable cables or buses, or the like. Local microprocessor-based control devices used to operate the components of each junction stage

* only need to offer a relatively low capacity

mitée and may include any of the various

fast microprocessors available on the market.

An example of such microprocessors is the LSI-11 marketed by DEC Incorporated of Boston,

Massachusetts, USA; according to a variant, a unit con-

venable can be assembled from the 2900 series of parts of.AMD Co. Similarly, the

main junctions and discs 12 and 16 which ensure

rent the "sequentialization" and the "deequentialization" of information can be standard units,

such as the block multiplexer, model 370 available

nible at IBM Corporation of Armonk, New York, ESUA.

Similarly, an IBM block multiplexer can be used for direct memory access, the actual connection of the various units being well.

known to specialists.

Likewise, the buffers 30 and 40 used for temporary storage of data in the main trunk and disk stages 12 and 16 can be of any suitable type although, in a presently preferred embodiment, one uses one. memory of at least 64 K bytes. A commercially available buffer of this type is manufactured by Fairchild Seriiconductor; it includes a memory to

direct access to N'-MOS with a speed of 200 nanoseconds.

The fast memory 22 which serves as a shelter or data cache must be of the type generally called "fast access memory", that is to say having a duration of.

cycle of 400 nanoseconds or less. In a way of realizing

preferred embodiment, the high-speed shelter has a

tee of 16 million bytes. A particular memory

A commercially available material suitable for use with the invention is manufactured by Intersil Corp., Sunnyvale, California, USA, and is distributed by Storage Technology Corp. of Louisville, Colorado, USA, Filing the present application; this memory is referred to as "model 3758" or

"model 3768".

Fig. 3 is a functional representation of the operation of the device according to the invention in a "read" mode, in which the main computer

10 requested information from memory.

The control signals are represented by solid lines and the flow of data by

dashed lines. As a result, the computer

main tor 10 transmits a command signal to the opera-

human heart to ask for certain information (for

example "mount N band") and given that the computer

main tor 10 "assumes" that the data is stored

on tape in sequential form, only the identi-

initial fication or "label" needs to be specified.

Other elements of the virtual storage device

tuelle, in particular the control processor 24,

respond to information by accessing all data

born that correspond to the requested information and in

causing this data to be assembled in a separate form.

quential.

-15 -

The main computer 10 therefore calls simple-

the N band of which it "assumes", in accordance with the in-

training provided by the individual program it is running, that it contains a particular set of data. In fact, in the case of the virtual storage device according to the invention, this particular data set may be distributed over a number of different disks and / or may be located at a number of locations on a same disk. As a result, the storage device

virtual machine according to the invention responds to an order at the

rator such as "mount N band" by searching in its own memory to indicate by data where the di-

to parts of the recording that the computer

main denominated 'band N' have been stored, the re-

The response of the device does not therefore consist in inciting a

operator to mount the N band but simply to

ler information about the location or locations

placements of the dataset identified by the

denomination "N band" from its own memory.

When the main junction stage 12 in-

indicates that an instruction "mount tape N" has been executed.

tee, which is practically instantaneous by comparison

with the mounting of a real tape, the main computer

pal 10 transmits a command to junction 12 to designate the specific identity of the information block to be read. This order is transmitted directly from the disk junction stage 12 to the control processor 24 which identifies the various areas in which the information is.

stored. This result can be achieved through the use of

tion of a data logger 46 coupled with the

ordering party. In an ac-

Most preferably, the data logger 46 is

takes direct access memory (RAM) (which can be supplemented as a backup by an unwinder unit -16-

tape and associated tape in the event of loss of

memory in RAM) in which the locations of the various sub-blocks of data which together constitute the data requested by the main computer 10 are recorded.

Once the locations of the various sub-

blocks of data have been identified on behalf of the control processor 24, signals are applied to the "control device" parts of the various stages

junction of discs 16, after which access to the data

The data is then transferred to the buffer of the trunk stage 16 and is prepared for transmission to the shelter or main memory 22 to reside there temporarily until whatever they are

required for the various main junction floors 12.

When buffer 40 is full of data,

a signal is transferred from the dis-

ques 16 to the control processor 24 to indicate this fact and, at this time, the control processor 24

transmits the buffered information directly to an es-

space previously allocated for this purpose in the shelter or

fast main memory 22.

With the tape devices of the art

earlier, the initial "editing" operation takes

usually about 30 s to 50 min. The total time required

required to execute a "read" command varies between 1 and 10 milliseconds depending on the characteristics of the device

individual and, of course, depending on the length of the

record read. In a preferred embodiment of the virtual storage device shown, a

operation "assembly" generally takes less than a second.

count. The actual "read" operation takes general-

ment 1 to 10 milliseconds as before, depending on the length of the recording and the characteristics of the shelter 22. Consequently, at this point, the information which should have been read will have been very quickly placed in shelter 22 where it is stored until a signal from memory junction 12 indicates to the shelter that the main computer is ready to receive data. At this point, the data has then been collected from the various points of the various disks 20 where it has been stored, has been sequentially formatted in the proper order and is ready to be transferred.

in the main computer 10 without a delay of

training or research of information on the di-

to disks. It is therefore clear that the

memory according to the invention offers temporary advantages.

Realities compared to disks and that, compared to tape devices, it completely avoids delays in assembly time. In this way, the "early buffering" provided by the use of the shelter combines the advantages of disk and tape in that it combines the lack of editing that disks allow with the sequential structure of the tapes, which saves time for the main computer as the data is completely organized in the vault. At the same time, thanks to the superior organization and cooperation of the various elements,

a very small fraction of the disk memory actually

tive is assigned to control a reading activity.

reading / writing or updating or saving data in this fraction, sometimes referred to as the "working area" factor of disk storage capacity. As a result, a much higher percentage of effective disk memory

is available for data. In this way, the ef-

Storage efficiency of disk memory can be

raised to a level similar to that of the band.

In the main "write" mode shown -18-

in Figure 4, the procedure is substantially the reverse

se of that of the "reading" mode which has just been described.

As in Fig. 3, the control signals are shown

felt by solid lines and the flow of data by broken lines. When the main computer 10 signals, by means of conventional tape drive codes, that it wishes to "write" or record data, this command is transmitted, via the trunk stage 12, to the processor of the machine. command 24. The latter commands at junction 12

to acknowledge receipt of the order and at the same time inter-

roge the disc junction stages 16 in order to find

worm a buffer 40 suitable for accepting all or part of the data. When such locations are determined, they are recorded in the data logger 46

by the control processor 24.

The control processor 24 then controls

at the main junction floor 12 to accept data

from the main computer 10 and direct them to appropriate locations in the data buffer 50 of the main trunk stage 12. If the buffer 30 becomes full before a corresponding space is available in the buffers 40 of

junction stages of disks, an instruction "affect-

ter space "is transmitted by the control processor to memory vault 22, after which data from

of the main junction stage buffer are applied

ceded to this memory vault 22. At a certain later

However, when a suitable buffer capacity is available in one or more disk trunk stages 16, the control processor commands the vault 22 to transmit the stored data to the buffers 40 of the appropriate disk trunk stages 16 in turn. view of their arrangement on the disks

associated disk units 20.

-19-

When applying each data block

born at a main junction 32 by the main computer

cipal 10, the memory junction module 34 determines

o, in the associated buffer 30, the new information

received will be stored; compresses the data sequentially so as to produce, for example, eight

data channels, and adds one or more bits of i

identification in the information block to indicate the size of it. In this way, data is continuously transmitted to the buffers 30 until

whether a given data block is complete or up to

until the main computer generates a signal

indicating the end of a given record. Under an im-

aspect of the invention, such a signal is inter-

lent by the local controller 28 as an end of message signal after which no further space

buffer memory does not need to be allocated.

At this point, the command processor 24 di-

writes the data now stored in data buffer 30 to fast shelter 22. During the time in which the main computer is storing data

in data buffer 30, as described above

However, the control processor 24 can "search" for sufficient space on the disk drives 20 and can allocate that space to the then-hearth data stored in the data buffer 30. Thus, when the end of signal data is received in the data from the control processor, this can be "sequenced" and transmitted to the quick shelter which serves as temporary storage space and can then be transferred to the disk drives 20 for viewing.

of their storage.

In other words, when the main computer

cipal produces an initial order "up band", that is

say prompts the operator to provide a blank tape for data storage purposes, this command is transmitted, through the main trunk stage

12, to the control processor 24. The control processor

command 24 responds to the instruction "mount tape" by

singing space on one or more disks 20 and reserving suitable space in one or more of the buffers 40 of the disk junction stages. This done,

the control processor 24 controls the ring stage

main tion 12 to accept data from the computer

principal factor 10, to "deequentialize" them and

store in the associated buffer 30. Once this tam-

pon is full, if no other buffer space is available, this data is transmitted to memory location 22. When sufficient disk space is available,

the next step is that the control processor

command 24 control at the junction of discs 42 of the

junction disk 16 write the data to the associated disk drive 20, after which the junction module 44 reads and "sequentializes" the information by placing it in the associated buffer 40, where it is located. written

on the associated disk drive 20. We will understand sisé-

that another possibility is to reproduce or

to memorize the data on a conventional tape drive

sic if, for example, a duplication is desired

saddle; in other words, the storage device

tion of data according to the invention can be connected in parallel with a conventional tape device of

prior art if desired.

Specialists will easily understand that jO the association of a rapid shelter with a control processor, together with junction stages

main and disc junction and with mo-

associated control modules, allows to combine the advantages of the tape and disk devices of the prior art; more precisely, accessibility -21-

easy disk drives is combined with the efficient

storage city for tape drives, which allows obtaining an extremely efficient and fast "virtual storage device" in which, thanks to the invention, a disk device "appears" to the central processor as a tape drive. band, but without

the disadvantages of it. Since the dis-

memory ques according to the invention are permanently mounted

manence, an intervention by an operator is not necessary.

required when a tape-type recording (i.e.

i.e. sequential recording) is desired. Further, prior art disk drives

can be used with the memory device

virtual option according to the invention without modification; that is to say that the device according to the invention can be considered as an inserted unit or junction

between a main computer of the prior art

re and prior art disk drives.

Consequently, it is not necessary to modify the

disk drives or the main computer for

see making them work in conjunction with the dis-

positive virtual storage according to the invention.

In addition, it will be noted that the virtual storage device according to the invention can be

used to establish a link entered any number

any main computers and any number

disk drives. Consequently, it will be easily understood

sure that if an operator has several computers

main nators and a limited number of units of

discs, the virtual storage device follows

before the invention can be used to ensure a

maximum storage efficiency and eliminate a multi-

unwanted plication of remote memory devices

ques or tape. The following main junction units

prior to the invention can be coupled with several main computers. Further, it will be appreciated that the presence of a fast memory or cover is essential for the early buffering which is a very important feature of the invention. Using the fast cover as an intermediate buffer between the junction of the invention. main computer and the various floors of

disk drive junction, the buffer can be

multiplex data swimming; in other words, according to the in-

vention, data stored at a number of times

placements on a number of disk drives

(what we can call "storage in the random form

roof ") can be assembled," sequenced "and stored temporarily in the rapid shelter until

that they are called by the main computer.

In this way, no delay is necessary for the transfer of the information from the memory to the main computer. Similarly, data

outputs from the main computer can be arranged

managed, divided and stored in the quick shelter until various disk storage areas are

available to store information.

A particularly important possibility

offered by the storage device according to the invention

tion is data compression. Until now, a common technique of data compression, which may involve replacing a long string of numeric "1" or "0" with symbols indicating the length of the string, could not be used.

with disk drives, given that this technology

nique was compressing the addressing information as well

that data. Now, given that, according to the invention

tion, disk drives take on the appearance of tape, this prior art difficulty is

eliminated and data compression is made com-

compatible with disk storage. Preferably, the data compression is performed in the control stage.

main junction, that is, during an operation

In writing ration, long continuous strings of "1" or "t0oi" can be detected and replaced with shorter symbols; during a read operation, these symbols are detected and replaced by the data

thus defined.

Finally, of course, the invention is null.

ment limited to the particular preferred embodiment

shown and described; she is susceptible to many

its variants without deviating from the mind for that

nor within the scope of the invention.

l -24-

Claims (19)

- CLAIMS - 1 - Data storage device intended for use with at least one main digital computer, said device being characterized in that it comprises: at least one main junction unit capable, in response to orders from of said main digital computer or of said calculations main digital lators, to store informa- tion arranged in sequential form or to access such information, said unit or each of said units comprising a first data buffer for storing data received from said main digital computer or from said main digital computers or directed to it or these; a central memory trale; at least one disk unit, said unit or each of said units comprising a plurality of disks capable of storing digital information and a second data buffer coupled with the considered disk unit and with said main memory for storing received data of said disk drive in question or directed towards it; and a unit of control coupled with said main junction units cipale and discs to ensure reception and ac- ceptation, by the main junction unit or units pale, of data in sequential form and for per- cause the drive (s) to store information in random form and access this information in the same form. 2 - Data storage device for For use in conjunction with one or more mainframe computers and one or more disk drives, said device being characterized in that it comprises: a data "shelter" (or cache) including a fast memory unit; a number of main computer trunk stages, at least equal to the number 2468 1 63 -25- main computers and each comprising an available local control device and junction means for coupling the main computer junctions with the main computer (s) and with the data shelter; a number of disk drive junction stages each including a local controller and junction means for coupling the jonc- tion of disk drives considered with drives of associated disks and with data shelter; and a dis- positive control to coordinate operation main computer junction stages, Disk drive and data shelter junction management born. 3 - Data storage device such as claimed in one of claims 1 and 2, characterized in that it responds equally well to orders operator than to machine orders. 4 - Data storage device such as claimed in one of claims 1 and 2, characterized in that it further comprises means data compression and decompression means data. - Data storage device as claimed in claim 2, characterized in that each main computer junction stage pal includes a data buffer. 6 - Data storage device as claimed in claim 2, characterized in that each disk drive junction stage includes a data buffer. 7 - Method for storing digital data risks, characterized in that it understands the operations consisting of: receiving said data in a mes- central memory; to determine storage locations appropriate kage on disk storage units; to -26_ transmit said data to junction units of disks associated with said remote storage units ques; and writing said data from said disk junction units to said disk memory units. 8 - The method of claim 7, ca- characterized in that the flow of data between said disk storage units and said main memory is controlled by a controller 9 - The method of claim 8, ca- characterized in that the control device responds both to operator orders and to ma- China. - Method according to claim 7, ca- characterized in that said data is received at from a main computer by a ring unit main tion and are 'deequentialized' 'earlier- ment to their transmission to the central memory, then "resequentialized" prior to their writing to disk storage units. 11 - Method according to one of claims 7 and 10, characterized in that it further comprises a data compression operation; 12 - The method of claim 7, charac- terized in that the addresses of the storage locations kage to which the data is stored on the uni- discs are stored in a memory direct access. 13 - The method of claim 12, ca- characterized in that said addresses are furthermore en- stored in other memory means. 14 - Process for retrieving data born stored on a plurality of disk storage units, characterized in that it comprises the operations consisting of: determining where said data is stored -27- kées; to retrieve said data from the- say disk memory units and have them write in a central memory; to put the said donations born into a queue in said main memory; and causing said data to be transmitted to a main computer. - Method according to claim 14, ca- characterized in that said data is "disequentia- read "before being written to the main memory and are" resequentialized before being transmitted to the main computer. 16 - Method according to one of claims 14 and 15, characterized in that it further comprises a data decompression operation. 17 - The method of claim 14, ca- characterized in that it further comprises an operation consisting in storing said data in a buffer interposed between the main memory and the main computer. 18 - The method of claim 14, ca- ractérisé in that the circulation of data between the disk drives, the main memory and the computer main is controlled by a controller. 19 - The method of claim 18, ca- characterized in that said control device responds both to operator orders and to ma- China. - Method of storing digital data risks, characterized in that it understands the operations consisting of: receiving data organized sequentially tiement of a main computer in main junction means; determining which portions of the disk storage means are available for the storage of said data; to subdivide said donations born in blocks corresponding to said portions; and to store said data in the form of blocks in the- say portions. 21 - The method of claim 20, characterized in that said data is "imbalanced tialized "in said main junction means. 22 - Method according to one of claims and 21, characterized in that said data is stored in a central memory before being stored kées in said portions. 23 - The method of claim 21, ca- characterized in that said data is compressed in said main junction means. 24 - The method of claim 20, ca- typified in that the addresses of the locations at which said data is stored are stored in direct access memory means. ___ - Method according to claim 20, ca- characterized in that the sequentially organized data- ment are also stored on memory means conventional belt.