JPH02307115A - Control system for storage subsystem - Google Patents

Abstract

PURPOSE:To increase the processing speed in the control system by making an access given to a replaceable storage medium look like a magnetic tape device and performing successively the accesses with no designation of addresses. CONSTITUTION:A storage subsystem 1 consists of plural decks 12 (121 - 12N) to which a replaceable storage medium is mounted and a storage subsystem control part 11. The part 11 includes a deciding logic part 110 and a control information storage part 111. Then an access given to the replaceable storage medium capable of a random access e.g. a rewritable optical disk, etc., look like a magnetic tape device. Thus the accesses are successively carried out with no designation of addresses. As a result, a function is available to improve the efficiency of a data storage of large capacity like a compressing function, etc. Then the processing speed is increased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an external storage device in an information processing system, and in particular to an external storage device using a randomly accessible removable storage medium such as a rewritable optical disk medium. The present invention relates to a control method for a storage subsystem that performs sequential data reading and writing (hereinafter referred to as sequential mode) that performs read/write access to an information recording area position next to the immediately previous accessed position without specifying an address.

[Prior art]

In general, in information processing systems, depending on the characteristics of the file being created, it is advantageous to use the direct access method, which allows for faster random access, and for some files, it is more advantageous to use the direct access method, which allows for faster random access, while others are mainly sequential access.

Additionally, there are files that can be expected to significantly reduce their data storage capacity by adopting a data compression function. Currently, the former uses magnetic disk devices and current optical disk devices, and the latter uses magnetic tape devices. In particular, the latter device is used when downloading files, etc., because the file size is large and the data storage capacity can be expected to be significantly reduced by mainly using sequential access or by using a data compression function. .

A typical conventional storage device using a removable medium is a magnetic tape device. magnetic tape device.

It is assumed that sequential access is performed, starting from the first information, and information regarding addresses is a tape mark.

BOT (start of tape), EOT (end of tape), and tape mark (file delimiter) are the only inputs that normally allow access to the storage area immediately after being read or written in the previous access. At this time, the software does not issue a positioning command for address specification when reading or writing, but rather issues it on the assumption that the immediately following storage area will be accessed. Also, when accessing the latter half of a file when storing a multi-file, there is a command that instructs you to skip that block, but in this case, even the file delimiter information (tape mark) is read. Positioning is performed by skipping sequential data.

With this method, there is no need to be aware of the size of the data written just before, and the data will continue to be written until there is no more storage space available.
Sequential access is possible. This allows easy control even when the data length is not clear in advance for files that are accessed sequentially, or when the data length cannot be determined until writing due to the data compression function in the storage subsystem. This has the advantage that the equipment capacity can be used effectively. In fact, this type of storage subsystem, which also has a compression function, has already generated σU and has a low bit price, making it ideal for storing large-capacity files.

[Problem to be solved by the invention]

However, when multiple files are stored, in order to access the later files, it is necessary to sequentially skip and position the data up to the file delimiter information (tape mark). 2. After information access is completed, it is always necessary to rewind, and this time is long, so it is desired to shorten this time.

On the other hand, a rewritable optical disk device, which is a typical example of a removable storage medium that can be accessed sequentially or directly, has a media capacity of 300 megabits (
MB), which outperforms current magnetic tape devices, and has a low bit cost, making it a promising alternative to magnetic tape devices.

However, many of the current rewritable optical disk devices are
Although it has a spiral-shaped data track (one continuous data track from the outside to the inside of a circle), making it more similar to a magnetic tape device than a magnetic disk device, it still emphasizes random access. To do this, FBA addressing is used, which formats a data block with a fixed length and sets the block address from the beginning of the data block. Prior to accessing data, a command and read command specifying the address position are used. It uses a direct access method that specifies write operations. Further, when a rotating body storage medium is used, depending on the timing of access, it may not always be possible to access the storage area immediately after the target storage area if the storage area is accessed without specifying an address. For this.

As it is, it cannot be used like a magnetic tape device, and a positioning command must be issued.

In addition, it is designed with emphasis on high-speed random access, and there is a problem in that it does not incorporate techniques that effectively reduce bit costs, such as compression mechanisms, rather than being conscious of the format.

The present invention has been made to solve the above problems.

An object of the present invention is to provide a storage subsystem using a randomly accessible removable storage medium (for example, a rewritable optical disk), in which access to the storage medium is
The object of the present invention is to provide a control system that pretends to be a magnetic tape device and performs sequential access without specifying addresses.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means for Solving the Problems] In order to achieve the above objects, the present invention provides a storage medium capable of reading and writing data sequentially and reading and writing data by random addressing. A removable storage medium in which an area unit is divided into blocks that can be located using relative or absolute addresses from the beginning.

In a storage subsystem comprising a plurality of read/write devices that mount the storage medium and a control device that controls them, when the storage medium is mounted, the control device moves the medium to the first writable storage device. Positioned in the area,
After that, read/write access is executed, and when the access is completed, the control device stores the current address information of the storage area where the access was executed, and each time it receives a read or write instruction for the same medium,
The most important feature is that the current address information is used to locate the next consecutive storage area.

[For production]

According to the above-mentioned means, storage media such as rewritable optical disks can be accessed sequentially like a magnetic tape device, while taking advantage of the original function of random access. , When the storage medium is mounted, it can be positioned at the first writable storage area, and each time a read or write instruction for the same medium is received, it can be positioned at the next consecutive storage area.

[Embodiments of the invention]

An embodiment of the present invention will be specifically described below with reference to the drawings.゛In all the figures for explaining the embodiment, parts having the same functions are given the same reference numerals, and repeated explanations thereof will be omitted.

FIG. 1 is a block diagram showing the overall schematic configuration of a storage subsystem according to an embodiment of the present invention.

In the figure, the storage subsystem 1 includes a plurality of decks 12 (121 to 12N) on which removable storage media are mounted.
and a storage subsystem control unit 11, the storage subsystem control unit l! 1 judgment logic section 110 and control information storage section! It consists of 11.

FIG. 2 is a detailed configuration diagram of the main parts of the system shown in FIG.
It consists of

In addition, the storage unit 111 stores information on each deck (121 to 12N).
Corresponding to this, it is composed of a storage table 112 that stores the control information storage area 21 and a table 113 that stores address information of the storage area that has been accessed immediately before.

FIG. 3 shows the specific structure of the control information in the removable storage medium, where 211 is an information storage area indicating the order of file delimiters (tape marks), and 212 is the start address of each file. The area 213 stores the final address of each file.

Next, the operation of the storage subsystem configured in this way will be explained.

(1) When the removable storage medium 2 is mounted on the deck 12, the control unit 11 of the storage subsystem 1 reads the removable medium white information storage area 21, and the removable storage medium corresponding to each deck in the control device is read. It is stored in the control information storage section 1!1 of the type storage medium. As explained earlier, the control information storage area 21 contains: (1) information indicating the order of file delimiters (tape marks) on the storage medium (storage area 211); (2) information on the starting storage area address of each file ( Memory area 2
12) , ■Final storage area address information (storage area 213) of each file is recorded. In addition, in the control information storage unit 111 of the replaceable storage medium corresponding to each deck,
Table 112 that stores control information (storage area) 21
and a table 113 that stores address information (current address information) of the storage area that was accessed immediately before.The initial value of the table 113 is:

Set to '0'. Here, the first storage area address "0"
' is logically BOT (
begin of tape), and the user information area 20 and the control information storage area z1 as a replaceable medium.
The boundary address is logically managed as the EOT (end of tape) of a conventional magnetic tape device.

(2) When the storage medium has been positioned at the first storage area address '0', the control unit 11 of the storage subsystem reports to the host device that access is now possible. The host device accesses this storage medium, but if the positioning has changed (orientation has changed) by the time the access is made, for example, it requests a retry of the command. , access will be granted once the positioning is completed again. These controls are executed by the control unit 11 according to predetermined rules.

When the first read/write (READ/WRITE) access is completed, the control unit sets the address in the current address information section 113 of the control information storage section Ill, and when the next access occurs, the address is set immediately after this storage area. This part is accessed by instructing the positioning in the storage area using an internal command.

In this case as well, if a command cannot be received while orientation is being established, use the command retry function etc. to update the storage subsystem so that the command can be received once orientation is complete. The control unit 11 establishes synchronization.

(3) If the storage subsystem receives an instruction to skip to the next internal file delimiter (tape mark), the file delimiter in the removable media control information storage area 21 The block address to be accessed is read from the information indicating the order of symbols (tape marks) (storage area 211) and the first storage area address information (storage area 212) of each file, and the block address is directly positioned at that address. If this tape mark information is not recorded in the removable medium control information storage area 21, the control unit 11 uses the last address information (storage area 213) in the removable medium control information storage area zl. After creating new address information in the removable medium control information storage area 21, the file is directly positioned at the top address based on this information.

(4) When the storage subsystem 1 receives a command to update the stored user information, it processes all recorded information, including the address information (storage area) 21, as having been updated. .

(5) When the storage subsystem 1 receives an instruction to dismount a storage medium, information indicating the order of delimiters (tape marks) of updated files;
Store the start storage area address information of each file on storage medium 2.
After writing to the control information area 21 of , the dismount operation is executed.

Although the explanation has been given using a rewritable optical disk medium as an example of a removable storage medium, a removable storage medium that can be read and written in both a sequential mode and an addressing mode is especially suitable for storage. It does not limit the type of media.

The present invention has been specifically explained above based on examples, but
It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit thereof.

〔Effect of the invention〕

As described above, according to the storage subsystem control method of the present invention, in a storage subsystem using a removable storage medium (for example, a rewritable optical disk, etc.),
It becomes possible to control access to a storage medium by pretending to be a magnetic tape device and performing sequential access without specifying an address.

This makes it possible to obtain a first-order effect.

(1) It becomes possible to utilize functions designed to improve the efficiency of large-capacity data storage, such as a compression function, making it possible to increase media storage capacity and speed up processing.

(2) By using the random access function, it is possible to shorten the access and rewind time to the beginning position of each file in a multi-file volume, and the processing time can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall schematic configuration of a storage subsystem according to an embodiment of the present invention. FIG. 2 is a detailed configuration diagram of main parts of the system shown in FIG. 1. FIG. 2 is a diagram illustrating a specific configuration of control information within. In the figure, 1... Storage subsystem using a replaceable storage medium, 11... Storage subsystem control unit, 110...
・Determination logic unit of storage subsystem control unit, 111・
. . . Control information storage unit for removable media, 112 . . . Storage table of control information 21 for each removable media,! 13... Memory table of addresses that were accessed immediately before, 12.
...A device W that mounts a removable medium and performs reading and writing.
t (deck) group, 121 to 12N...Each deck capable of independent operation, 2...Replaceable storage medium, 20...User information area, 21...Control information storage in replaceable storage medium Area, 211... Information storage area indicating the order of file delimiters (tape marks), 212...
Start storage area address information storage area for each file. 213...Final storage area address information storage area for each file

Claims (1)

[Claims] (1) Sequential reading and writing of data and data reading and writing by random addressing are possible, and the unit of storage area as a storage medium is positioned using a relative address from the beginning or an absolute address. a removable storage medium that is divided into possible blocks;
In a storage subsystem comprising a plurality of read/write devices that mount the storage medium and a control device that controls them, when the storage medium is mounted, the control device moves the medium to the first writable storage device. Positioned in the area,
After that, read/write access is executed, and when the access is completed, the control device stores the current address information of the storage area where the access was executed, and each time it receives a read or write instruction for the same medium,
A storage subsystem control method characterized in that the current address information is used to position the next consecutive storage area.