JPH07306757A - Library system - Google Patents

Abstract

PURPOSE:To provide the library system which is improved in access performance. CONSTITUTION:When a replaceable optical disk medium 5 stored in the storage area 6 of a warehouse 3 is moved to a drive part 2 by a hand part 4 and a conveyance control part 9, and a data block recorded on the optical disk medium 5 is accessed, a hierarchical constitution controller 8 manages the frequencies of access to all data blocks recorded in the library system and the optical disk medium 5 to copy and record data blocks, which are high in frequency of access among all the data blocks recorded in the optical disk library 1, to a cache 7 according to the frequencies of access by as many as blocks can be stored, and then the optical disk media 5 on which data blocks high in the frequency of access following the data blocks recorded in the cache 7 are recorded is arranged according to the frequencies of access to the data block from the part closest to the drive part 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed library system provided with a cache memory capable of reading and writing data at high speed for a library system which accommodates a plurality of exchangeable recording media and selectively reads and writes data. is there.

[0002]

2. Description of the Related Art An optical disc device is a storage device capable of exchanging an optical disc medium having a storage capacity of several hundred MB for an optical disc medium having a diameter of 90 mm and about 1 GB for a disc medium having a diameter of 130 mm, and exchanging the optical disc medium. Is equivalent to a storage device having an infinite storage capacity.

In recent years, taking advantage of the characteristics of this optical disk device, an optical disk library has been developed which automatically replaces an optical disk medium and provides a storage capacity of 1 TB class. The optical disc library includes one optical disc medium.
A large number of standard disc cartridges each containing a single disc are stored in a warehouse, and the cartridges are moved to an optical disc drive by an automatic handling mechanism to read / write data.

However, in the case of the optical disk drive, in order to replace the cartridge, it is necessary to first return the cartridge loaded in the optical disk drive to the warehouse, and then convey the desired cartridge stored in the warehouse to the optical disk drive. is there. Further, the cartridge has a drawback that the average access time including replacement of the cartridge of the access library reaches a dozen seconds.

As a method for overcoming these problems, as disclosed in "Aggregation type optical disk device access method" of Japanese Patent Laid-Open No. 3-94342, a cache memory composed of a magnetic disk device or the like is connected to a library device. ,
A method is known in which a data block having a high access frequency is redundantly recorded in a cache memory to reduce the access frequency to an optical disk device and improve the access performance of a library device.

[0006]

However, even in the above-described method using the cache memory, if the optical disk device is accessed without hitting the cache memory, the access performance inherent to the optical disk device is exposed. Further, if there is a significant difference in access performance between when the cache memory is hit and when it is not hit, not only the system design becomes difficult, but also the user is uncomfortable. Therefore, it is desired to improve not only the access performance for the data blocks recorded in the cache memory which are frequently accessed but also the access performance for all the data blocks recorded in the library.

In view of the above problems, it is an object of the present invention to provide a library system with improved access performance.

[0008]

In order to achieve the above object, the present invention provides a plurality of exchangeable recording media, a warehouse capable of accommodating a plurality of the recording media, and data of the recording media. In a library system including a drive unit for reading and writing data, and a conveying unit for exchanging a recording medium loaded in the drive unit with an arbitrary recording medium stored in the warehouse, all data blocks recorded in the recording medium From a cache memory composed of a non-commutative high-speed memory for copying and recording the number of frequently accessed data blocks in the order of access frequency, and all the data blocks recorded on the recording medium and the recording medium. A hierarchical controller that manages access frequency and transfers data between the recording medium, cache memory, and host device; Drive the conveying means based on the management content of the storage controller, and transfer control means for arranging the recording medium in the warehouse in the order of access frequency of the recording medium from the nearest of the drive unit, and the hierarchical controller, When a data block is copied from the recording medium to the cache memory, the access frequency of the copy source data block is transferred to the copy destination data block, and the access frequency of the copy source data block is set to 0. A library system is proposed in which, when a data block is erased or a data block is written from the cache memory to the recording medium, the access frequency of the write source data block is added to the write destination data block.

According to a second aspect, in the library system according to the first aspect, a library system is proposed in which the maximum access frequency of a plurality of data blocks recorded on the recording medium is used as the access frequency of the recording medium. To do.

[0010]

According to claim 1 of the present invention, the hierarchical controller manages all the data blocks recorded on the recording medium and the access frequency of the recording medium, and also records all the data blocks recorded on the recording medium and the recording frequency. Data blocks with high access frequency of the medium are copied and recorded in the cache memory in the order of access frequency. Further, when a data block is copied from the recording medium to the cache memory by the hierarchical controller, the access frequency of the copy source data block is transferred to the copy destination data block and the copy source data block is transferred. When the block access frequency is set to 0 and the data block is erased from the cache memory or the data block is written from the cache memory to the recording medium, the access frequency of the write source data block is the write destination data. Granted to blocks. Further, the transportation control means drives the transportation means based on the management contents of the hierarchical controller, and the recording media are arranged in the warehouse in the order of access frequency of the recording media from the nearest position of the drive unit for reading and writing data on the recording media. It As a result, the recording medium in which the data block having the next highest access frequency is recorded next to the data block recorded in the cache memory is arranged in the order of the access frequency of the data block from the nearest position of the drive.

According to a second aspect of the present invention, the access frequency of the recording medium is the maximum value of the access frequencies of the plurality of data blocks recorded on the recording medium.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention.
In the figure, 1 is an optical disk library, 2 is a drive unit, 3 is a warehouse, 4 is a hand unit, 5 is an optical disk medium stored in a cartridge, 6 is a storage area for storing the optical disk medium 5, and 7 is a magnetic disk device or A cache memory (hereinafter referred to as a cache) configured by a non-commutative high-speed memory such as a semiconductor memory, 8 is a hierarchical controller, and 9 is a transport control unit.

The drive unit 2 is an optical disk drive device arranged below the warehouse 3 having a plurality of storage areas 6, and is adapted to read / write data from / to the optical disk medium 5.

The optical disk medium 5 is movably stored in the storage area 6 by the transport control unit 9 via the hand unit 4, and becomes accessible by the hierarchical controller 8 when loaded in the drive unit 2.

The hand unit 4 moves between the drive unit 2 and the warehouse 3 to carry, load, and take out the optical disk medium 5. The specific structure is shown in FIG.
As shown in. That is, to the side of the drive unit 2 and the warehouse 3, a vertical movement mechanism 4a for moving the hand unit 4 in the vertical direction along the warehouse 3, and a horizontal movement for moving the hand unit 4 in the front-back direction with respect to the warehouse 3. The mechanism 4b is installed.

The vertical moving mechanism 4a movably supports the hand portion 4 on a vertically extending guide shaft 4c. For example, a motor (not shown) incorporated in the hand portion 4 and a gear meshing with the guide shaft 4c The part 4 is adapted to move in the vertical direction.

The horizontal moving mechanism 4b supports the vertical moving mechanism 4a on a horizontally movable driving unit 4d, and the vertical moving mechanism 4a is moved forward and backward by a motor or cylinder (not shown) connected to the driving unit 4d. To move to. That is, the vertical movement mechanism 4a moves the hand unit 4 to the position of the drive unit 2 or an arbitrary storage area 6 of the warehouse 3, and the horizontal movement mechanism 4b moves the hand unit 4 supported by the vertical movement mechanism 4a. The optical disk medium 5 can be taken in and out of the storage area 6 of the drive unit 2 or the warehouse 3 by moving it in the front-back direction. Note that the moving mechanism of the hand unit 4 shown in FIG. 2 is an example, and this is not the case in actual design.

The operation of the hand section 4 is controlled by a program stored in the transfer control section 9, and the transfer control section 9 is controlled.
Performs drive control of the hand unit 4 based on the access frequency of each optical disc medium 5 managed by the layered controller 8, that is, the access frequency determined by the number of times the optical disc medium 5 is loaded into the drive unit 2 within a predetermined time. There is.
For example, a specific identification number is assigned to each optical disk medium 5, and in the hierarchical controller 8, which storage area 6 in the warehouse 3 stores the optical disk medium 5 based on each access request. Is managing. In addition, the date and time when an access request is made for each data block recorded on each optical disk medium 5 is stored, and the number of times of access from the latest access request to a certain period before is set as the access frequency of the data block. There is.

Further, in order to improve the access performance of the library system, the hierarchical controller 8 uses the cache 7
All the access frequencies of the data blocks recorded on the optical disk medium 5 in the optical disk library 1 are managed, and the data blocks with high access frequency are copied from the optical disk library 1 to the cache 7. Further, it also plays a role of erasing a data block whose access frequency is relatively low in the cache 7 or writing it in the optical disk library 1.

Next, the operation of this embodiment having the above-mentioned configuration will be described with reference to the flow charts shown in FIGS. 3 and 4 are flowcharts showing the flow of data block control by the hierarchical controller 8.

The hierarchical controller 8 updates the access frequency of all data blocks at regular intervals by a normal timer interrupt (S1) (S2). Although the method of obtaining the access frequency is outside the scope of the present invention, the predicted access frequency is calculated from the number of times the data block is accessed per unit time and the elapsed time after the data block is accessed using the prediction curve as shown in FIG. The method of obtaining is common.

Further, when comparing the access frequencies of the data blocks in order to prevent the careless replacement of the data blocks and the rearrangement of the disk media, a hysteresis characteristic is provided so as not to respond to a fine access frequency difference. Has been devised.

On the other hand, an access request from a host device (not shown) is accepted as an event interrupt by the hierarchical controller 8 (S3), and it is first checked whether a desired data block exists in the cache 7 (S4). ). As a result of this check, if the desired data block is present in the cache 7, the data block is immediately read and the access frequency of the data block is updated (S5).

If the desired data block is not in the cache 7, the optical disk library 1 is accessed (S6) and the desired data block is in the cache 7.
And the access frequency of the data block is updated (S7), and whether or not the data should be copied to the cache 7 is determined based on the access frequency (S8).
As a result of this determination, if it is determined that the desired data block has a high access frequency and should be copied to the cache 7, the data block read by the optical disk drive is transferred to the host device via the bus. At the same time, it is written in the cache 7. At this time, the access frequency of the data block is transferred to the data block in the cache 7 copied from the optical disk medium 5 on which the data block was recorded, and the data block of the copy source left on the optical disk medium 5 is transferred. The access frequency is set to 0 (S9). At this point, the data block is effectively excluded from the access frequency update target.

Next, the total capacity of the data blocks copied in the cache 7 is calculated, and it is judged whether or not the data blocks in the cache 7 should be swept out to the optical disk library 1 (S10). If the result of this determination is that the calculated value has reached the specified value, the data block with the lowest access frequency in the cache 7 is selected (S1).
1), returned to the optical disc library 1. At this time, it is determined whether or not this data block has been updated in the cache 7 (S12), and if it has been updated,
The optical disc library 1 is accessed (S13),
The updated data block is overwritten on the original data block on the optical disc medium 5, and at the same time, the access frequency of the data block is transferred from the cache 7 to the optical disc medium 5 (S14).

As a result of the determination in S12, if the data block is not updated in the cache 7,
The data block is erased in the cache 7, and only the access frequency is passed from the cache 7 to the optical disk medium 5 (S15). At this point, the optical disk medium 5 is virtually
The upper data block is subject to access frequency update again.

Although the access frequency data is described as being recorded in the cache 7 or the optical disk medium 5 together with the data block, the access frequency data is actually stored in the hierarchical controller 8. It is stored in a rewritable non-volatile memory or the like provided and is centrally managed.

On the other hand, the optical disk library 1 manages all the access frequencies of the optical disk medium 5 and also makes the addresses of the storage areas 6 floating so that the optical disk media 5 can be rearranged in the order of access frequency (S1).
6). The access frequency of the optical disk medium 5 is set to the maximum value of the access frequency of the data blocks in the optical disk medium 5. This shortens the time required for the access frequency management process. For example, it is possible to use the average value of the access frequencies of a large number of data blocks recorded on the optical disk medium 5 as the access frequency of the optical disk medium 5, but it takes a lot of time to calculate the access frequency. At the same time, the hit rate of the cache 7 may decrease.

Although the method of address floating is out of the scope of the present invention, generally, if the addresses are floated and the optical disk media 5 are arranged in the order of access frequency, the access performance of the optical disk library 1 is improved, but the optical disk media 5 are The processing of rearranging in the order of access frequency becomes an overhead. This overhead occurs because the hand unit 4 cannot handle a plurality of optical disc media 5 at the same time.

Here, in order to reduce this problem, the optical disk medium 5 is managed in group units. FIG. 6 shows the simplest configuration example, in which the optical disk medium 5 stored in the warehouse 3 of the optical disk library 1 is divided into two groups in the order of access frequency, and data blocks with high access frequency are recorded. The optical disc medium 5 in which the first group G is close to the drive unit 2
The optical disc medium 5 which is placed in No. 1 and is rarely accessed is placed in the second group G2. However, within the group, the optical disk medium 5 is stored at an arbitrary position regardless of the access frequency.

In this system, the first group G1 has at least one free storage area, and the accessed optical disk medium 5 stored in the drive unit 2 prior to the access of the optical disk medium 5 is stored in this free storage area. Then, the desired optical disk medium 5 is accessed.
When the desired optical disk medium 5 is in the first group G1, the desired optical disk medium 5 is driven after the optical disk medium 5 in the drive unit 2 is returned to the warehouse 3 as shown in a to c in the figure. The part where the optical disk medium 5 is pulled out after being conveyed to the section 2 becomes a new empty storage area. In this case, rearrangement of the optical disk medium 5 is not performed.

When the desired optical disk medium 5 is in the second group G2, the accessed optical disk medium 5 in the drive unit 2 is set to the first group as shown by d to i in the figure.
After storing the desired optical disk medium 5 in the empty storage area of the group G1 and transporting the desired optical disk medium 5 to the drive unit 2, the second optical disk medium 5 with the lowest access frequency in the first group G1 is transferred.
The optical disc medium 5 of the group G2 is stored in the pulled-out portion.

This is a basic method for rearranging the optical disk media 5 in order of access frequency. Even when the number of groups is increased in order to improve the access performance of the optical disk library 1, the optical disk media 5 are automatically rearranged in the order of access frequency when the method is sequentially repeated and an empty storage area is created in the first group G1. ing.

Although the floating address method has been described above, in the present embodiment, the access frequency of the data block copied to the cache 7 is set to 0 on the copy source optical disk medium 5. Therefore, when a data block is copied to the cache 7, the access frequency of the optical disc medium 5 of the copy source is instantly lowered, and the data is transferred to a group far from the vicinity of the drive unit 2. As a result, the optical disk medium 5 recording the data block with the highest access frequency next to the data block copied in the cache 7 is automatically arranged in the vicinity of the drive.

When the time for re-accessing the data block in the cache 7 becomes long and the access frequency decreases, the data block is returned from the cache 7 to the optical disk medium 5. In this case, the optical disk medium 5 which is located in the group far from the drive unit 2 after copying the data block to the cache 7 inherits a relatively high access frequency from the cashier 7, and therefore the group near the drive unit 2 for a while. Will be located in.

As described above, in the present invention, the data block with the highest access frequency is recorded in the cache 7, and the data block with the second highest access frequency is automatically arranged in the vicinity of the drive unit 2. Therefore, the highest access performance can always be maintained.

In the present invention, the access performance for all data blocks in the optical disk library 1 is improved by the following two effects.

The first effect is due to the floating address method, and since the optical disk medium 5 that is frequently accessed is arranged near the drive unit 2, the average moving distance of the hand unit 4 is greatly shortened. is there.

The second effect is that the access frequency of the optical disk medium 5 on which the data block is transferred to the cache 7 is drastically reduced and the optical disk medium 5 is moved away from the vicinity of the drive unit 2, so that the average movement distance of the hand unit 4 is further shortened. There is a point.

For ease of explanation, it is assumed that one data block is recorded on one optical disk medium 5 as shown in FIG. In the conventional method shown in FIG. 7A, when a frequently accessed data block is copied to the cache 7, the optical disk medium 5 on which the data block is recorded will not be accessed, so that the warehouse 3
It becomes as if a plurality of empty storage areas had occurred inside.

On the other hand, as shown in FIG.
Since the floating address method is adopted in this embodiment, the optical disk medium 5 in which a data block is copied to the cache 7 and the access frequency is set to 0 is moved to a position farthest from the drive unit 2 for reading and writing data. Become.
As a result, the number of optical disc media to be handled is effectively reduced, and the average movement distance of the hand unit 4 is reduced. As is apparent from FIG. 7, the effect of the present invention becomes more remarkable as the capacity of the cache 7 is increased in order to improve the access performance of the library system.

Although the optical disk is illustrated as the storage medium in the present embodiment, the present invention is not limited to this, and the present invention can be applied to a magnetic disk or a magnetic tape. Further, although the optical disk medium 5 housed in the cartridge is conveyed in the above embodiment, the storage medium may be conveyed directly. Further, the warehouse for storing the storage medium may have not only the storage areas arranged in the vertical direction but also the storage areas arranged in the horizontal direction. In this case, the hand unit 4 (conveying means)
Need only be configured to move vertically and horizontally.

[0043]

As described above, according to the first aspect of the present invention, the copying which is copied to the cache memory by combining the floating address system in which the recording medium having a high access frequency is arranged in the vicinity of the drive unit with the cache memory is copied. By setting the access frequency of the original data block to 0,
The data block with the highest access frequency is recorded in the cache memory, and the data block with the next highest access frequency is automatically placed in the vicinity of the drive section. High access performance can be maintained. In particular, the effect becomes more remarkable as the capacity of the cache memory is increased in order to improve the access performance of the library system.

Further, according to claim 2, in addition to the above effect, the access frequency of the recording medium is the maximum value of the access frequencies of the plurality of data blocks recorded in the recording medium. The time required for the management process is reduced, and the access performance can be further improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a library system according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an optical disk library according to an embodiment.

FIG. 3 is a flowchart showing a flow of data block control according to an embodiment.

FIG. 4 is a flowchart showing a flow of data block control according to an embodiment.

FIG. 5 is a diagram showing a prediction curve of access control.

FIG. 6 is a diagram showing a configuration example when managing disk media in group units.

FIG. 7 is a diagram showing an example of recording a data block on an optical disc medium.

[Explanation of symbols]

1 ... Optical disk library, 2 ... Drive section, 3 ... Warehouse, 4 ... Hand section, 5 ... Optical disk medium, 6 ... Storage area, 7 ... Cache, 8 ... Hierarchical controller, 9 ... Transport control section.

Claims (2)

[Claims] 1. A plurality of exchangeable recording media, a warehouse capable of accommodating a plurality of the recording media, a drive unit for reading and writing data of the recording media, and a recording medium loaded in the drive unit in the warehouse. In a library system having a transport means for exchanging an arbitrary storage medium stored therein, a data block having a high access frequency is copied from all data blocks recorded on the storage medium in an order of access frequency and recorded. A cache memory composed of a non-commutative high-speed memory for managing all data blocks recorded on the recording medium and the access frequency of the recording medium, and between the recording medium, the cache memory, and the host device. A layered controller for transferring data, and driving the carrying means based on the management contents of the layered controller, A transfer control means for arranging the recording medium in the warehouse in the order of access frequency of the recording medium from the vicinity of the drive unit is provided, and the hierarchical controller copies the data block from the recording medium to the cache memory. The access frequency of the original data block is transferred to the copy destination data block, the access frequency of the copy source data block is set to 0, and the data block is erased from the cache memory or the data block is deleted from the cache memory. A library system characterized in that, when data is written to a data block, the access frequency of the data block of the writing source is added to the data block of the writing destination. 2. The library system according to claim 1, wherein a maximum value of access frequencies of a plurality of data blocks recorded on the recording medium is used as the access frequency of the recording medium.