JPH01255028A - Method for making access to external storage device - Google Patents

Abstract

PURPOSE:To shorten a time required for access to an external memory device by reading out plural blocks comprising one file from plural memory devices complementarily, respectively, and reading the file by reconstructing one file. CONSTITUTION:When it is required to continue the plural blocks logically to render the files stored in magnetic disk devices A12 and B13, a CPU 1 uses a file managing program 4, and issues the readout request of a first block (a) to be continued to the device 12 via a first disk controller 10. Simultaneously, the CPU issues the retrieval request of the physical cylinder address of the next block (b) to the device B13 via a second disk controller 11. And when the readout of the block (a) is completed, the retrieval request of the physical cylinder address of a third block (c) is issued to the device 12, and when the readout of the block (a) is completed and the retrieval of the block (b) is also completed, the readout of the block (b) is requested to the device B13. Next, the readout of the block (c) is requested similarly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of accessing an external storage device such as a magnetic disk used in a computer system.

A general management system for conventional magnetic disks is shown in FIG. In the figure, 1 is a CPU in a computer system, 2 is a main memory, and 3 is an operating system that operates on the main memory 2.
system (hereinafter abbreviated as O8), 4 is a file management program included in the above O83 as a file management means;
7 is a magnetic disk device provided as an external storage device;
6 is connected to the CPU 1.6 via the system bus 5. A disk control device connected to the main storage device 2, 8 is a disk device 7
The block (memory unit) 9 is a block map indicating whether the block 8 is used or not, and this block map 9 is rewritten each time a file is stored or erased.

The operation will be explained below.

When the file management program 4 generates a file on the magnetic disk device 7, the recordable unused blocks 8 usually have physical continuity lost due to erasure, re-recording, etc. Unused blocks 8 on a magnetic disk device 7 are searched from a block map 9, and each is used in logical succession. Therefore, conventionally, the method of accessing the magnetic disk device 7 under the above-described disk management system has been to access the physical cylinder address of each block in response to an input/output request.

Problems to be Solved by the Invention In such conventional access methods, there is no problem when one block constitutes one file, but when multiple blocks are logically contiguous to constitute one file. In this case, physical cylinder addresses are usually not consecutive between blocks, so when you finish input/output processing for one block and try to access the next block, as shown in Figure 4, the physical cylinder addresses of that block are In order to search for an address, seek operations within the magnetic disk device take time, which increases access time and reduces the throughput of the computer system.

The present invention has been made to solve these conventional problems, and aims to provide an access method that reduces the overhead caused by physical operations such as seek operations when accessing an external storage device. .

Means for Solving the Problems A method for accessing an external storage device according to the present invention provides a method for accessing an external storage device in a computer system that includes a plurality of external storage devices having the same storage content and a plurality of controls that control input/output of the external storage devices. It is characterized by having multiple devices, distributing input/output requests to each device, and always accessing them simultaneously.

Effects of the present invention By providing a plurality of external storage devices with the same storage content, input/output processing can be distributed, and by accessing each at the same time and performing physical operations in parallel, input/output overhead can be reduced. The throughput of a computer system can be increased.

Example An embodiment of the present invention will be described below.

In FIG. 1, 1 is a CPU in an electronic computer system;
2 is the main memory, and 3 is O8.3 operating on the main memory 2.
4 is a file management program included in O83; 12.
13 is a magnetic disk device A and B having the same storage content provided as an external storage device; 10.11 is a magnetic disk device A;

1.B, which controls 12 and 13; The second disk controller is connected to C'P U 1 and the main storage device 2 via the system bus 5 .

Next, the operation of magnetic disk devices A, B, and 1 will be explained.
In order to reproduce the files stored in 2.13,
When multiple blocks need to be logically consecutive,
Using the file management program 4, the CPUI issues a read request for the first block a to be made consecutive to the disk device A12 via the first disk control device 10. At the same time, a search request for the physical cylinder address of the next block b is issued to the magnetic disk device B13 via the second disk control device 11. When the reading of block a is completed, a search request for the physical cylinder address of the third block C is issued to the magnetic disk device A12 via the first disk control device 10, and a request for retrieving the physical cylinder address of the third block C is issued to the magnetic disk device A12 via the first disk control device 10. When the search for block b is completed, a read request for block b is issued to the magnetic disk device B13 via the second disk control device 11. Furthermore, when the reading of block b is completed and the search of block C is completed, the first disk controller N
10, block C is transferred to the magnetic disk device A12.
issue a read request. two magnetic disk devices A,
For B and 12.13, by continuing to repeat this operation, physical operations such as seek operations can be processed in parallel, so the overall access time can be shortened. FIG. 2 shows a time chart for these operations.

In addition, when updating the storage contents of the magnetic disk device, writing-related processing is required, but the CPU 1 uses the file management program 4 to update the storage contents of the magnetic disk device A12 via the first disk control device 10. A write request is simultaneously issued to each magnetic disk device B13 via the two disk control devices 11. Since the two disk devices are accessed separately, a backup can be taken each time the storage contents of the magnetic disk device are updated, without increasing the access time.

Note that in the above embodiment, the explanation was made assuming that two external storage devices are connected as magnetic disk devices.
The present invention is applicable to various external storage devices for the main storage device, such as flexible disks, magnetic tapes, and optical disks, and a configuration in which not only two but three or more devices are connected is also possible.

Effects of the Invention As explained above, the present invention provides a method for reading a file composed of multiple blocks by connecting multiple external storage devices that store the same content and accessing them simultaneously. The access time can be shortened, and each time the storage contents of the external storage device are updated, a backup can be taken with the same access time as before.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram according to one embodiment of the present invention, FIG. 2 is an operation time chart diagram of the same embodiment, FIG. 3 is an operation explanatory diagram explaining a general disk management method, and FIG.
The figure is an operation time chart according to a conventional disk access method. 1...CPU, 2...Main storage device, 3
...Operating system, 4...
... File management program, 5 ... System bus, 10.11 ... First and second disk control devices, 12.13 ... Magnetic disk device.

Claims (1)

[Claims] In a computer system having an external storage device that can store information such as a program or data as a file, when reading one file from multiple external storage devices, multiple blocks constituting the one file in the memory are read. The access time to the external storage device is shortened by reading data from the plurality of external storage devices in a complementary manner, and reconstructing and reading the one file from the data of the plurality of read blocks. How to access external storage devices.