JPH07295761A - Mirroring magnetic disk device - Google Patents

Abstract

PURPOSE:To accelerate processing speed by respectively parallelly processing different operations such as write cache processing at one device and read processing at the other device when executing write cache at two mirroring magnetic disk devices. CONSTITUTION:This device is composed of magnetic disk devices 1 and 2 and connected through a magnetic disk controller 3 to a central processing unit 4. When writing data, the same data are written in both the magnetic disk devices 1 and 2 by the controller 3 and when reading data, the data are read from any one magnetic disk device where no error is generated. When a write command completes data reception, command completion is decided but when a read instruction is received during the write cache to continue data write in a medium even after the command completion, the write cache operation is temporarily stopped and reading is performed by fixing only one of two magnetic disk devices 1 and 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control means for reducing the waiting time for reading data from a write cache and a mirroring magnetic disk device having the control means.

[0002]

2. Description of the Related Art Conventionally, in a mirroring magnetic disk device, since only safety is emphasized, the second magnetic disk device controls only the same operation at the same time as a backup of the first magnetic disk device, and therefore the write operation is performed. Even if a read command was received in the cache, the read could not be executed while the two magnetic disk devices were executing the write cache, and the processing time at this time increased.

A known example of the prior art is Japanese Patent Laid-Open No. 62-086.
No. 425 is known.

This conventional magnetic disk device with a mirroring function will be described with reference to the drawings.

FIG. 3 is a block diagram of a conventional magnetic disk device with a mirroring function.

This conventional magnetic disk device with a mirroring function has a central processing unit 31 and a write data bus 32.
And a disk address bus 33, a magnetic disk controller 34, and magnetic disk devices 42 and 43. The magnetic disk controller 34 includes a disk address queue 35, a disk cache 36, a disk address register 37, and Device / address data selection control circuit 38, address selection circuit 39, and data selection circuit 4
0, a disk write control circuit 41, a write data register 44, and an instruction interpretation execution control circuit 45.

The disk address and write data from the central processing unit 31 are respectively transferred to the disk address queue 35.
Since the data is also stored in the disk cache 36, the same data is written in the magnetic disk devices 42 and 43 when the write operation is executed in the magnetic disk device 43. When the selection control circuit 38 confirms the completion of the write operation of the magnetic disk device 42, the address selection circuit 39 selects the disk address, the data selection circuit 40 selects the write data, and the disk write control circuit 41 selects A write operation is performed on the magnetic disk device 43. In other words, when the operating system issues a data write command only once, the same data is written in the magnetic disk device 42 and the magnetic disk device 4.
Will be written in 3. As a result, the disk access time can be shortened.

As described above, in the conventional example, the two magnetic disk devices perform the same operation at the same time, but in the present invention, when the two magnetic disk devices receive a read command in the write cache, another operation is performed. There is a difference in doing.

[0009]

In the above-mentioned conventional mirroring magnetic disk device, the two magnetic disk devices always perform the same operation, so that the read operation can be performed until the two magnetic disk devices complete the write cache. However, there is a problem that the read instruction processing time in the write cache is long.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and to execute a write cache process on one of two magnetic disk devices that are mirrored and a read process on the other. By performing different operations in parallel, the processing speed can be increased.

Therefore, when the read command is received in the write cache, the mirroring magnetic disk device of the present invention interrupts the write cache process of one of the mirrored magnetic disk devices and processes the read command. It is characterized by resuming the processing of the write cache that was interrupted after the end.

Specifically, the mirroring magnetic disk device of the present invention has two magnetic disk devices, a first magnetic disk device and a second magnetic disk device, and both of them are used when writing data. When writing the same data to the disk device and reading the data, in the mirroring magnetic disk device having means for reading the data from the magnetic disk device that does not generate an error, the command reception is completed upon completion of the write command data reception, and even after the command completion , When the read command is accepted during the write cache that continues to write data to the medium, only the first magnetic disk device is fixed and the write cache operation is temporarily suspended.
It is characterized by having a means for reading.

The mirroring magnetic disk device of the present invention is characterized in that when a read command is received in the write cache, only the second magnetic disk device is fixed and the write cache operation is temporarily suspended to perform a read operation. There is.

The mirroring magnetic disk device of the present invention, when a read command is received in the write cache,
It is characterized in that only the magnetic disk device having the larger amount of unwritten data has a means for temporarily suspending the write cache operation and reading.

The mirroring magnetic disk device of the present invention, when a read command is received in the write cache,
Only the magnetic disk device having the less unwritten data has a means for temporarily suspending the write cache operation and reading.

[0016]

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

FIG. 1 is a block diagram of an embodiment of a mirroring magnetic disk device according to the present invention, and FIG.
2 is a flowchart showing control when the mirroring magnetic disk device of FIG. 1 receives a read command.

In FIG. 1, the mirroring magnetic disk device of this embodiment comprises magnetic disk devices 1 and 2 and is connected to a central processing unit 4 through a magnetic disk controller 3.

The magnetic disk devices 1 and 2 are written by the control device 3 to the same data in both magnetic disk devices when writing data, and when reading data, the magnetic disk device or the data that does not generate an error is read. It is a mirroring magnetic disk device. Each of the magnetic disk devices 1 and 2 is provided with a write cache function of completing the command upon completion of data reception of the write command and continuing the medium writing even after the command is completed.

Next, the control when the read command is accepted in the mirroring magnetic disk device of this embodiment will be described with reference to FIG.

Step 21 is a judgment as to whether or not the two magnetic disk devices are executing the write cache.
Step 22 is a judgment of the magnetic disk device selection for interrupting the write cache and executing the read command. In step 23, write cache interruption control is performed. Step 24 is the execution of the read command. Step 25 is control for restarting the write cache suspended in step 23. Step 26 is the same control as the conventional read,
Step 27 is the same control as the conventional write cache.

When the mirroring magnetic disk device embodying this embodiment receives a read command, it determines in step 21 whether this device is executing the write cache. At this time, if it is not being executed, the process proceeds to step 26 where the read process similar to the conventional one is performed, and the command is terminated. In step 22, the magnetic disk device that executes the read command is selected. In this embodiment, the two magnetic disk devices are the magnetic disk device 1 and the magnetic disk device 2, and the magnetic disk device 1 is unconditionally read. The disk device 2 is assigned to the conventional write cache process.

The magnetic disk device 1 suspends the write cache in step 23 and stores the address, parameter and data required for disk control at that time. In step 24, the read command is actually executed. In step 25, the write cache process is restarted and ended by the address, parameter, and data stored in step 23.

The magnetic disk device 2 performs write cache as in the conventional case, but ends without executing read processing.

Next, other claims of the present invention will be described.

In the case of claim 2 of the present invention, the determination in step 22 of FIG. 2 unconditionally selects the magnetic disk device 2. Therefore, the magnetic disk device 2 processes the read command, and the magnetic disk device 1 processes the write cache.

In the case of claim 3 of the present invention, the determination in step 22 of FIG. 2 selects that the magnetic disk device having the larger amount of unwritten data in the write cache performs the read. Then, the magnetic disk device with less unwritten data can execute the write cache process while the magnetic disk device with more unwritten data is executing the read. As a result, since the mirroring magnetic disk device puts more emphasis on the write cache process, the write access time can be shortened.

In the case of claim 4 of the present invention, the determination in step 22 of FIG. 2 selects that the magnetic disk device having the less unwritten data in the write cache performs the read. Then, the magnetic disk device with the larger amount of unwritten data can execute the write cache process while the magnetic disk device with the smaller amount of unwritten data is reading. As a result, the mirroring magnetic disk device puts more emphasis on the read processing, so that the read access time can be shortened.

[0029]

As described above, the mirroring magnetic disk device of the present invention has the mirroring function by assigning one of the two mirrored magnetic disk devices to the read command even during the write cache processing. As a result, the reliability of data can be increased, and the processing time of the device can be shortened by shortening the data access time of the read instruction during the write cache.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a mirroring magnetic disk device according to the present invention.

FIG. 2 is a flow chart showing control when the mirroring magnetic disk device of FIG. 1 receives a read command.

FIG. 3 is a configuration diagram of a conventional hard disk device with a mirroring function.

[Explanation of Codes] 1 magnetic disk unit 2 magnetic disk unit 3 magnetic disk controller 4 central processing unit 31 central processing unit 32 write data bus 33 disk address bus 34 magnetic disk controller 35 disk address queue 36 disk cache 37 disk address Register 38 Device / address data selection control circuit 39 Address selection circuit 40 Data selection circuit 41 Disk write control circuit 42 Magnetic disk device 43 Magnetic disk device 44 Write data register 45 Instruction interpretation execution control circuit

Claims (4)

[Claims] 1. A magnetic disk device comprising two magnetic disk devices, a first magnetic disk device and a second magnetic disk device. When writing data, the same data is written to both magnetic disk devices and when reading data. , In a mirroring magnetic disk device that has means for reading data from the magnetic disk device that does not generate an error, the command is completed when the write command data has been received, and data writing to the medium continues even after the command is completed When the read command is received, the mirroring magnetic disk device is provided with means for temporarily fixing the write cache operation while fixing only the first magnetic disk device. 2. When the read command is received in the write cache, only the second magnetic disk device is fixed and the write cache operation is temporarily interrupted to provide a read operation. Mirroring magnetic disk device. 3. When the read command is received in the write cache, only the magnetic disk device having a large amount of unwritten data temporarily suspends the write cache operation to perform a read operation. The described mirroring magnetic disk device. 4. When the read command is received in the write cache, only the magnetic disk device having a smaller amount of unwritten data temporarily suspends the write cache operation to perform a read operation. The described mirroring magnetic disk device.