JPH0786809B2 - Multiplexing control method for external storage device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention relates to a multiplexing control method for an external storage device, and an object thereof is to improve the multiplexing processing speed. A multiplexing control method for an external storage device, comprising a multiplexing control device for performing the same data write process and reading data to one of the external storage devices at the time of reading, When the device shifts from the writing process to the reading process, the device is configured to perform the reading process on the external storage device for which the writing process is finally completed.

[Industrial application field]

The present invention relates to improvement of a multiplexing control system for an external storage device.

In a conventional multiplexing system of external storage devices such as a magnetic disk device, when a plurality of external storage devices are set as main and secondary and a write command (write command) is output, all external devices The same data is written in the storage device, and when a read command (read command) is output, the data is always read from the main external storage device.

However, in order to synchronize the data, the read processing cannot be performed unless the write processing of all the multiplexed external storage devices is completed. Therefore, the SCSI (Small Computer Syste
m Interface), an interface that requires bus acquisition processing to access an external storage device,
Even if the write command has a read command chained to the command chain, the bus must be released once to terminate the write processing of the other secondary external storage devices when the write processing of the main external storage device is finished, and therefore, the write processing is restarted. A bus for the main external storage device is acquired and read processing is performed.

Therefore, even if the command chain is performed, the number of bus release / acquisition processes increases and the processing speed decreases. Therefore, there is a demand for a multiplexing control method for an external storage device that improves this.

[Conventional technology]

FIG. 4 is an explanatory view of the prior art and shows an example of a multiplexing system of a magnetic disk device.

In this system, one of the multiplexed magnetic disk devices is used as a main magnetic disk device, and when an error occurs in the main magnetic disk device, one of the other sub magnetic disk devices is used as a new main magnetic disk device. A magnetic disk device is used, and the multiplexing control channel device 3 is omitted in the figure.
The SCSI is controlled, and the multiplexing control of these magnetic disk devices is performed based on the command received from the host device 2.

For example, when a write command is received, a bus acquisition process is first performed to acquire a right to use the SCSI bus (hereinafter referred to as bus 30) for the main magnetic disk device 5, and the data stored in the main storage device 1 is transferred to the controller 10 After transferring to the main magnetic disk unit 5 via the
Release 30.

Similarly, the bus acquisition process is sequentially performed on the plurality of sub magnetic disk devices 6 to transfer the same data.

In this way, when the write command is received from the host device 2,
Write processing is performed on all the multiplexed magnetic disk devices 5 and 6.

In a magnetic disk device or the like having a low processing speed, so-called ejection control is performed. For example, the main magnetic disk device 5
The bus 30 is once released at the point of time when the command transfer is performed, the bus 30 for the other secondary magnetic disk device 6 is acquired, and the write processing is performed. In the magnetic disk device that was pushed out,
After the internal processing is completed, the bus 30 is acquired and becomes ready for the next data transfer. This enables parallel processing,
Unless the bus is released by the multiplexing control channel device 3 at the end of the write process, the bus 30 remains occupied by the released magnetic disk device, and the bus acquisition process for other magnetic disk devices becomes impossible. .

On the other hand, upon receiving the read command, the multiplexing control channel device 3 reads the data after acquiring the bus for the main magnetic disk device 5, and then releases the bus 30.

If the read command is chained to the write command, the bus 30 for the main magnetic disk device 5 is acquired after the write processing to all the multiplexed magnetic disk devices 5 and 6 is completed. Execute the read command.

[Problems to be Solved by the Invention]

In the multiplex system of the external storage device, since the write data in the main storage device 1 is guaranteed, the read process can be performed only after the write process of all the multiplexed magnetic disk devices is completed.

Therefore, even when the read command is output by being chained to the 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 the other sub magnetic disk devices is completed. After that, the bus 30 for the main magnetic disk device 5 is again acquired and the read command is executed, and there is a problem that the bus acquisition processing increases and the processing speed decreases.

Therefore, the write process of the main magnetic disk device may be executed last, and the read command may be executed without opening the bus 30, but for example, the magnetic disk devices to be multiplexed are connected to different buses, In addition, in a system in which there are a plurality of host devices that access the magnetic disk device, a bus acquisition wait occurs, and it is difficult to always end the write processing of the main magnetic disk device 5 last and efficiently.

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 the multiplexing processing speed.

[Means for Solving the Problems]

FIG. 1 In the principle diagram of the present invention, 21a and 21b are a plurality of multiplexed external storage devices, and 20 is a multiplexing control device, and when the write process shifts to the read process, the external device that has finished the write process last Read processing is performed on the storage device.

[Work]

When shifting from the writing process to the reading process by the command chain, the multiplexing control device 20 performs the reading process on the external storage device that has finished the writing process last.

As a result, the bus acquisition process for the read process is omitted and the processing speed is improved.

〔Example〕

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

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

FIG. 2 shows an example of a duplication system of magnetic disk devices (corresponding to the external storage devices 21a and 21b) 10a and 10b.
In the figure, 10a and 10b are duplicated magnetic disk devices, and there is no distinction between main and sub.

Reference numeral 1 denotes a main storage device, which is a storage area for write / read data,
A command storage area and the like are provided.

A higher-level device 2 issues a write / read command.

Reference numeral 13 is a multiplexing control channel device (corresponding to the multiplexing control device 20), and the magnetic disk device 10
Performs multiple write processing and read processing for a and 10b. If the command chain is a write command-read command, the magnetic disk unit 10
Of a and 10b, the read process is performed by the magnetic disk device that has completed the write process last. Therefore, the synchronization flags 22a and 22 for determining whether or not the write processing has ended
b is provided corresponding to the magnetic disk devices 10a and 10b.

In addition, the same reference numeral represents the same object throughout the drawings.

In the multiplexing system having the above configuration, when the read command is chained following the write command, the following processing is performed. See FIG. 3 (1) First, the bus 30 acquisition process for the magnetic disk device 10a is performed.

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

(3) After turning on the synchronization flag 22a at the end of the write process for 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 processing is not completed, so the bus 30 release processing for the magnetic disk device 10a is performed. If all are on, the last write processing is completed, so bus release processing is not performed. As it is, the magnetic disk device 10a performs the read process, and after the read process is completed, the bus release process for the magnetic disk device 10a is performed.

(5) Bus acquisition processing is performed on the magnetic disk device 10b. The bus acquisition process is performed when the magnetic disk device 10a is pushed out or when the bus is released after the write process of the magnetic disk device 10a is completed.

(6) After obtaining the bus, write processing is performed by the magnetic disk device 10b.

(7) At the end of the write process, the synchronization flag 22b is turned on, and it is verified whether all the synchronization flags 22a and 22b are on. If all are on, the last write process is completed, so the magnetic disk device 10b reads. Run the command,
If it is not on, the bus release process of the magnetic disk device 10b is performed for the magnetic disk device 10b.

As described above, the multiplexed magnetic disk devices 10a and 10b
Of these, since the read process is performed on either one of the magnetic disk devices that has finished the write process last, it is not necessary to perform the bus acquisition process for the read process, and therefore the processing speed is improved.

〔The invention's effect〕

As described above, the present invention provides a multiplexing control method for an external storage device in which the number of bus acquisitions is reduced, and the effect of enabling efficient multiplexing control is great.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a configuration diagram of one embodiment,
FIG. 3 is a schematic flow chart of the embodiment, and FIG. 4 is an explanatory view of the prior art. In the figure, 1 is a main storage device, 2 is a higher-level device, 3 and 13 are multiplexing control channel devices, 4 is a 10 controller, 5 is a main magnetic disk device, 6 is a sub magnetic disk device, and 10a and 10b are magnetic disk devices. , 20 are multiplexing control devices, 21a and 21b are external storage devices, 22a and 22b are synchronization flags, and 30 is a bus.

Claims (1)

[Claims] 1. When writing, the same data writing process is performed to all multiplexed external storage devices (21a, 21b), and when reading, the data reading process is performed to one of the external storage devices. A multiplexing control method for an external storage device comprising a multiplexing control device (20), wherein the multiplexing control device (20) finally ends the writing process when shifting from the writing process to the reading process. A multiplexing control method for an external storage device, characterized in that a read process is performed on the external storage device.