JPS6286425A - Magnetic disc control device - Google Patents

Abstract

PURPOSE:To reduce the disc access time by using one data write instruction from a central processing unit so as to write same data in two sets of magnetic disc devices. CONSTITUTION:Since a disc address and a write data from the central proc essing unit 1 are stored respectively also in a disc address queue and a disc cache 6, when write operation is executed to a magnetic disc device 13, the same data are written in the magnetic disc devices 12, 13. When a selection control circuit 8 confirms the end of write of the magnetic disc device 12, an address selection circuit 9 selects a disc address and a data selection circuit 10 selects a write data and a disc write control circuit 11 writes the magnetic disc device 13. That is, when the operating system gives a data write command only once, the same data is written in the magnetic disc devices 12, 13. Thus, the disc access time is decreased.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magnetic disk control device.

[Conventional technology]

When a magnetic disk drive fails in a computer system, the data on the failed magnetic disk drive becomes unusable, making it impossible to continue subsequent processing. For this reason, conventionally, the operating system writes the same data to two magnetic disk drives, and if one magnetic disk drive fails, processing is performed using the data from the other normal magnetic disk drive. It was continuing.

[Problem that the invention seeks to solve]

However, in the conventional method described above, the operating system had to execute data write commands to the two magnetic disk devices separately, so the overhead of the operating system degraded the performance of the central processing unit. The disadvantage was that the disk access time was long.

The present invention solves the above-mentioned drawbacks by causing the magnetic disk control device to write the same data to two magnetic disk devices when the operating system issues a data write command only once.

[Means for solving problems]

The magnetic disk control device of the present invention includes device selection means for selecting the first magnetic disk device of two magnetic disk devices that is predicted to finish the write operation earlier, and a device selection means for selecting the first magnetic disk device that is predicted to finish the write operation earlier, and for writing data from the central processing unit. The central processing 4I means that the same data can be written to the two magnetic disk devices with a single data write command from the device.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows one embodiment of the invention. When a data write command is issued from the central processing unit 1 to the magnetic disk controller 4 via the command path 4, the write data passes through the write data bus 2, and the disk address passes through the disk address bus 3. Then, they are each passed to the magnetic disk control device 4. The disk address is stored in the disk address register 7 and the disk address key-5 4, and the write data is stored in the write data register 14 and the disk cache 6.
is stored in

Under the control of a selection control circuit 8 that controls the selection of magnetic disk devices, addresses, 2, and data, a read address selection circuit 9 selects the contents of the disk address register 7 and inputs the selected contents to the disk write control circuit 11. , the data selection circuit 10 selects write data 1/register 14 as write data and inputs it to the disk write control circuit 11.

Under the control of the selection control circuit 8, the disk write control circuit 11 selects as the first of the two magnetic disk devices 12. Write write data to disk address.

Here, a procedure in which the selective opening circuit 8 selects the one that can be accessed faster from two magnetic disk devices will be explained. The selective WIJ circuit 8 sends a magnetic head position successive command to the magnetic disk device 12 and the magnetic disk device platform 13, respectively, and recognizes the position of the magnetic head.

By comparing the position information of the magnetic head indicating the cylinder position and rotational position 111 with the write address at which the write operation is to be performed, which is the output of the address withdrawal circuit 9, the selection control circuit selects the method as shown in FIG. (select the magnetic disk device that you can access).

FIG. 2 is a flow diagram showing the operation of the 8-selection control circuit 8.
In step 21, the difference 2, C13 between the current cylinder position of the magnetic head of each current magnetic disk device and the cylinder position of the write address is calculated. Stesoge 23
Then, the magnitude of the difference obtained in steps 21 and 22 is determined, and in step 24 and 25, the magnetic disk device with the smaller difference is selected as the first writing target device. In step 24, if the difference is negative, a total of 9γ is calculated using the X-adic system to obtain a positive value. However, X is the maximum value of the rotational position of the magnetic head. If the differences are equal, step 26.
27 Determine the magnitude of the current rotational position of the magnetic head of each magnetic disk device and the rotational position of the write address, and determine whether the current rotational position of the magnetic head is physically closer to the front of the rotational position of the write address. If it is or is equal to (
In fact, if they are equal including the overhead up to the start of write data transfer), the magnetic disk device 12 is selected as the first write target. If it is located further away than the other, the magnetic disk drive 13 is selected as the first write target.

Now, suppose that the first magnetic disk device 12 is predicted to be able to be accessed quickly using the method shown in FIG. This section explains the procedure for writing data with the same content as the loaded data.

As mentioned above, the disk address and write data from the central processing unit 1 are also stored in the disk address queue 5 and the disk cache 6, respectively, so this information is used to perform the write operation on the magnetic disk 6 and device 13. If you execute
The same data will be written to the magnetic disk drive 2 and the magnetic disk device 13.

When the selective f wholesale circuit 8 confirms that the write operation of the magnetic disk unit #12 is completed, the address selection circuit 9 selects a disk address from the disk address queue 5, and the data selection circuit 10 selects a disk address from the disk cache 6. select the included data. Based on the selected disk address and write data, the disk write control circuit 11 performs a write operation on the magnetic disk device 13.

In other words, when the operating system running on the central processing unit issues a data write command only once, the same data will be written to the magnetic disk device 12 and the magnetic disk device 13.

〔Effect of the invention〕

As explained above, the present invention takes advantage of the fact that the data written to the first magnetic disk device remains in the disk cache, and uses the data in the disk cache in the second magnetic disk device. By automatically writing data to the magnetic disk controller, the operating system can perform double writing to the magnetic disk device with a single data write command, instead of issuing two data write commands in the past. This has the effect of reducing the overhead caused by this, improving the performance of the central processing unit, and shortening the disk access time during dual writing.

Furthermore, when the disk duplex function is adopted in an operating system that does not yet have the disk duplex write function, there is an advantage that the operating system does not need to be modified at all.

Note that by selecting the device that is predicted to finish the write operation sooner from the two magnetic disk devices, an effect that the disk access time can be shortened occurs.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
FIG. 3 is a flow diagram showing the operation of the figure. 1...Central processing unit, 2...Write data bus, 3...--Disk address bus, 4...-
... Magnetic disk control device, 5 ... Disk address key, 6 ... Disk cache,
7-...Disk address register, 8...
---Selection control circuit, 9 --- Address selection circuit,
lO---Data selection circuit, 11---Disk write control circuit, 12---Magnetic disk unit, 13---Magnetic disk unit, 14------・
-・Write data register. [Figure 1 Figure 2

Claims (1)

[Scope of Claims] Device selection means for selecting a first magnetic disk device of two magnetic disk devices that is predicted to finish a write operation earlier, and a disk cache for writing data from a central processing unit. , a means for directly writing the data into the first magnetic disk device and a means for writing the data from the disk cache into the second magnetic disk device, and one data write from the central processing unit. A magnetic disk control device characterized in that it is possible to write the same data to the two magnetic disk devices by a command.