JPH0448321A - Multiplex control system for external storage device - Google Patents

Abstract

PURPOSE:To improve the multiplex processing speed by executing reading to an external storage device with which the write processing is ended finally when the write processing proceeds to the read processing. CONSTITUTION:A multiplex control channel device 13 performs the multiplex write and read processing operations to the magnetic disk devices 10a and 10b with the commands. When the write and read commands are chained to each other, one of both devices 10a and 10b that is ended with the write processing finally performs the read processing. Thus the bus acquiring operations required for the read processing can be omitted and the multiplex processing speed is improved.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a multiplexing control method for external storage devices, and aims to improve the multiplexing processing speed. A multiplexing control method for external storage devices including a multiplexing control device that performs write processing of the same data and performs data read processing for one of the external storage devices when reading data, the multiplexing control method comprising: The control device is configured to perform a read process on the external storage device where the write process was last completed when moving from the write process to the read process.

[Industrial application field]

The present invention relates to an improvement in a multiplexing control method for external storage devices.

In a conventional multiplexing system for external storage devices such as magnetic disk devices, multiple external storage devices are set as the main and secondary devices, and when a write command is output, all multiplexed external storage devices are The same data is written to the storage device, and when a read command is output, the data is always read from the main external storage device.

However, in order to synchronize data, read processing cannot be performed until the write processing of all multiplexed external storage devices is completed.
computer 5ystes + Interface
), in which bus acquisition processing is required to access an external storage device, even if there is a read command chained to a write command, the bus will be acquired once the write processing of the main external storage device is completed. must be released to finish the write processing of the other external storage devices, and therefore the bus for the main external storage device is acquired again and read processing is performed.

For this reason, even if command chaining is performed, the number of bus release/acquisition processes increases and the processing speed decreases.Therefore, there is a need for a multiplexing control system for external storage devices that improves this problem.

[Conventional technology]

FIG. 4 is an explanatory diagram of the prior art, showing an example of a multiplexing system for magnetic disk devices.

In this system, one of the multiplexed magnetic disk devices is used as the main magnetic disk device, and if an error occurs in the main magnetic disk device, one of the other secondary magnetic disk devices is used as the new main magnetic disk device. This is a magnetic disk device, and in the figure, the multiplex control channel device 3 is replaced by 5 (not shown).
It controls the C3I and performs multiplexing control of these magnetic disk devices based on commands received from the host device 2.

For example, when a write command is received, first the scs i bus (hereinafter bus 30
), and performs bus acquisition processing to acquire the right to use the main memory f.
After the data stored in the bus 30 is transferred to the main magnetic disk device 5 via the IO controller 4, a release command is sent to release the bus 30.

Similarly, bus acquisition processing is sequentially performed for a plurality of sub magnetic disk devices 6 to transfer the same data to each of them.

When a write command is received from the host device 2 in this way,
Write processing is performed on all multiplexed magnetic disk units f5 and f6.

Note that in a magnetic disk device or the like having a slow processing speed, so-called push-off control is performed. For example, the main magnetic disk device 5
When the command is transferred to , the bus 30 is temporarily released,
The bus 30 for other secondary magnetic disk devices 6 is acquired and write processing is performed. After the internal processing is completed, the ejected magnetic disk device acquires the bus 30 and waits for the next data transfer. This achieves parallel processing, but unless the multiplex control channel device 3 performs bus release processing at the end of the write process, the bus 30 will remain exclusive to the ejected magnetic disk device.
Bus acquisition processing for other magnetic disk devices becomes impossible. On the other hand, upon receiving the read command, the multiplex control channel device 3 acquires the bus for the main magnetic disk device 5, reads the data, and then releases the bus 30.

In addition, when a read command is command chained to a write command, after the write processing to all the multiplexed magnetic disk devices 5 and 6 is completed, the bus 30 acquisition processing for the main magnetic disk device 5 is performed. and execute the read command.

[Problem to be solved by the invention]

In a multiplexed external storage system, in order to guarantee the write data on the main storage 21, read processing cannot be performed until the write processing of all multiplexed magnetic disk devices is completed.

Therefore, even if a read command is output in a command chain with a write command, the bus 30 is temporarily released when the write processing of the main magnetic disk device 5 is completed, and the write processing of other secondary magnetic disk devices is finished. After that, the bus 3o for the main magnetic disk device 5 is acquired again and the read command is executed, resulting in an increase in bus acquisition processing and a decrease in processing speed.

Therefore, it is sufficient to execute the write process of the main magnetic disk device last and then execute the read command without releasing the bus 3o. However, for example, if multiplexed magnetic disk devices are connected to different buses, In a system where there are multiple host devices that access the magnetic disk device, a wait for bus acquisition occurs, and the main magnetic disk device 5
It is difficult to always finish the write process last and efficiently.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a multiplexing control method for an external storage device that improves multiplexing processing speed.

[Means to solve the problem]

In FIG. 1, a diagram of the principle of the present invention, 21a and 21b are multiplexed external storage devices, 20 is a multiplexing control device, and when moving from write processing to read processing, the external storage device that last completed the write processing is Performs read processing on the storage device.

[For production]

When the multiplexing control device 20 shifts from the write process to the read process by the command chain, it performs the read process on the external storage device that last completed the write process.

This eliminates bus acquisition processing for read processing, improving processing speed.

〔Example〕

Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram of the first embodiment, and FIG. 3 is a schematic flowchart of the embodiment.

FIG. 2 shows a magnetic disk device (external storage device 21a).

21b) shows an example of a duplex system of 10a and 10b. In the figure, 10a and 10h are dual magnetic disk drives, and there is no distinction between main and sub.

l is the main memory, a storage area for write/read data,
It has a storage area for commands, etc.

2 is a host device that issues write/read commands.

Reference numeral 13 denotes a multiplex control channel device W (corresponding to the multiplex control device 20), which performs multiple write processing and read processing for the magnetic disk device 10a and Rob according to command instructions. If the commands are chained such as a write command and a read command, the read process is performed by the magnetic disk drive that completed the write process last among the magnetic disk drives 10a and 10b. Therefore, the synchronization flags 22a and 22b for determining whether the end of the write process is the last one are set in the magnetic disk device 10a,
10b compatible.

In addition, the same reference numerals represent the same objects throughout the figures.

In the multiplex system configured as described above, when a read command is command chained following a write command, the following processing is performed. Refer to FIG. 3 (1) First, the bus 30 for the magnetic disk device 10a
Acquisition processing is performed.

(2) After acquiring the bus, write processing is performed in the magnetic disk device 10a.

(3) After turning on the synchronization flag 22a at the end of the write process to the magnetic disk device 10a, it is verified whether all the synchronization flags 22a and 22b are on.

(4) If all are on, the last write process has not finished, so perform the bus 30 release process for the magnetic disk device 10a. If all are on, the last write process has finished, so do not perform the bus release process. The magnetic disk device E10a continues to perform read processing, and after the read processing is completed, bus release processing for the magnetic disk device 10a is performed.

(5) Perform bus acquisition processing for the magnetic disk device lOb. This bus acquisition process is performed during release control of the magnetic disk device 10a or when the bus is released after the write process of the magnetic disk device 10a is completed.

(6) After acquiring the bus, write processing is performed using the magnetic disk device job.

(At the end of the write process, turn on the synchronization flag 22b, verify whether all the synchronization flags 22a and 22b are on, and if they are all on, the last write process has finished, and the read command is sent to the magnetic disk device 10b. is executed, and if it is not on, a bus release process for the magnetic disk device 10b is performed for the magnetic disk device 10b.

As described above, the multiplexed magnetic disk device 10a,
Since the read process is performed on one of the magnetic disk devices 10b that last completed the write process, there is no need to perform a bus acquisition process for the read process (therefore, the processing speed is improved).

In the figure, 1 is a main storage device, 2 is a host device, 3.13 is a multiplex control channel device, 4 is an IO controller, 5 is a main magnetic disk device, 6 is a sub magnetic disk device, 10a,
10b is a magnetic disk device, 20 is a multiplexing control device, 2
1a and 21b are external storage devices, 22a and 22b are synchronization flags, and 30 is a bus.

〔Effect of the invention〕

As described above, the present invention provides a multiplexing control method for external storage devices that reduces the number of bus acquisitions, and has a significant effect of enabling efficient multiplexing control.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of the present invention, Fig. 2 is a configuration diagram of an embodiment,
FIG. 3 is a schematic flowchart of the embodiment, and FIG. 4 is an explanatory diagram of the prior art. Figure 1 Figure 2 Schematic flowchart of the embodiment Figure 3

Claims (1)

[Claims] When writing, all multiplexed external storage devices (21
Write the same data to a and 21b),
A multiplexing control method for an external storage device, comprising a multiplexing control device (20) that performs data read processing for one of the external storage devices at the time of reading, the multiplexing control device (20) comprising: . A multiplex control method for external storage devices, characterized in that when moving from write processing to read processing, read processing is performed on the external storage device for which write processing has been completed last.