JPH0740219B2 - Magnetic disk controller - Google Patents

Description

The present invention relates to a magnetic disk control device.

[Conventional technology]

When the magnetic disk device fails in the electronic computer system, the data of the failed magnetic disk device becomes unusable, and it becomes impossible to continue the subsequent processing. Therefore, conventionally, the operating system writes the same data to two magnetic disk devices, and when one magnetic disk device fails, the data is processed from the other normal magnetic disk device. I was continuing.

[Problems to be solved by the invention]

However, in the above-mentioned conventional method, the operating system has to separately execute the data write command to the two magnetic disk devices, so that the overhead of the operating system lowers the performance of the central processing unit. However, there is a drawback that the disk access time becomes long.

The present invention eliminates the above-mentioned drawback because the magnetic disk control device writes the same data to two magnetic disk devices if the data write command is issued only once from the operating system.

[Means for solving problems]

The magnetic disk control device of the present invention includes a device selection means for selecting the first magnetic disk device of which the access operation is expected to be completed sooner based on a predetermined procedure among the two magnetic disk devices, and a central processing unit. A write data register and a disk cache for storing write data sent from the device, and the write data read from the write data register in the first magnetic disk device in response to a selection signal from the device selecting means. The second magnetic disk device is provided with write control means for writing the write data read from the disk cache.

〔Example〕

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

FIG. 1 shows an embodiment of the present invention. When a data write instruction is issued from the central processing unit 1 to the magnetic disk control unit 4 via the instruction path 4, the instruction interpretation execution control circuit
The data write command is recognized at 15 and the write data is passed to the magnetic disk controller 4 through the write data path 2 and the disk address through the disk address path 3. The disk address is stored in the disk address register 7 and the disk address queue 5, and the write data is stored in the write data register 14 and the disk cache 6.

Under the control of the selection control circuit 8 which controls the selection of the magnetic disk device, the address and the data, the address selection circuit 9 selects the content of the disk address register 7 and inputs it to the disk write control circuit 11. Further, the data selection circuit 10 selects the write data 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 writing control circuit 11 selects the one of the two magnetic disk devices 12 and 13 which is predicted to be accessed earlier as the first disk, and the disk designated by the disk register 7. Write the write data to the address.

Here, a procedure in which the selection control circuit 8 selects one of the two magnetic disk devices that can be accessed earlier will be described. The selection control circuit 8 sends a magnetic head position read command to the magnetic disk device 12 and the magnetic disk device 13, respectively, and recognizes the position of the magnetic head.

The selection control circuit determines the second by comparing the position information of the magnetic head indicating the cylinder position and the rotational position with the write address, which is the output of the address selection circuit 9, at which the write operation is desired to be performed.
Select the magnetic disk unit that can be accessed faster by the method shown in the figure.

FIG. 2 is a flow chart showing the operation of the selection control circuit 8.
In steps 21 and 22, differences C ₁₂ and C ₁₃ between the current cylinder position of the magnetic head of each magnetic disk device and the cylinder position of the write address are calculated. In step 23, the magnitude of the difference obtained in steps 21 and 22 is judged, and steps 24 and 25 are determined.
Then, the magnetic disk device having the smaller difference is selected as the first writing target device. In step 24, if the difference is negative, the value is calculated by the x-adic system and made a positive value. However,
x is the maximum value of the rotational position of the magnetic head. If the difference is the same, in step 26, it is judged whether the current rotational position of the magnetic head and the rotational position of the write address of each magnetic disk device is larger or smaller, and the current rotational position of the magnetic head is physically the write address. If the magnetic disk device 12 is located closer to the front than the rotational position or if they match (actually, if they also include the overhead until the start of write data transfer), the magnetic disk device 12 is set as the first writing target. Select (step 27). Also, if the current rotational position of the magnetic head is located far ahead of the rotational position of the write address, 1
The magnetic disk device 13 is selected as the first writing target (step 28).

Now, assuming that the first disk, which is expected to be accessed quickly by the method of FIG. 2, is the magnetic disk device 12,
Next, in the second magnetic disk device 13,
The procedure for writing the same data as the write data written in 12 will be described.

Since the disk address and the write data from the central processing unit 1 are also stored in the disk address queue 5 and the disk cache 6, respectively, as described above, the write operation is executed in the magnetic disk device 13 using these information. Then, the same data is written in the magnetic disk device 12 and the magnetic disk device 13.

When the selection control circuit 8 confirms the completion of the write operation of the magnetic disk device 12, the address selection circuit 9 selects the disk address from the disk address queue 5, and the data selection circuit 10 selects the write data from the disk cache 6. Select. Based on the selected disk address and write data, the disk write control circuit 11 causes the magnetic disk device to
Write to 13.

That is, when the operating system operating on the central processing unit issues a data write command only once, the same data is written in the magnetic disk device 12 and the magnetic disk device 13.

〔The invention's effect〕

As described above, the present invention utilizes the fact that the data written in the first magnetic disk device remains in the distor cache and uses the data in the disk cache in the second magnetic disk device. The magnetic disk controller automatically writes data by the operating system, so that the operating system enables double writing to the magnetic disk device with one data write command, and conventionally two data write commands are issued. This has the effects of reducing the overhead caused by this, improving the performance of the central processing unit, and shortening the disk access time during double writing.

Furthermore, when the disk double writing function is adopted in an operating system that does not yet have the disk double writing function, there is an effect that the operating system does not need to be modified.

It should be noted that by selecting one of the two magnetic disk devices that is expected to complete the writing operation earlier, the effect that the disk access time can be shortened is produced.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG.
It is a flowchart which shows the operation | movement of a figure. 1 ... Central processing unit, 2 ... Write data path, 3 ... Disk address path, 4 ... Magnetic disk controller, 5
... disk address queue, 6 ... disk cache, 7 ... disk address register, 8 ... selection control circuit, 9 ... address selection circuit, 10 ... data selection circuit, 11 ... disk write control circuit, 12 ... Magnetic disk unit, 13 ... Magnetic disk unit, 14 ... Write data register.

Claims (1)

[Claims] 1. A device selecting means for selecting a first magnetic disk device of which the access operation is expected to be completed sooner than the other magnetic disk device according to a predetermined procedure, and a central processing unit. A write data register and a disk cache for storing incoming write data, and the write data read from the write data register is written to the first magnetic disk device in response to a selection signal from the device selection means. The second magnetic disk device is provided with a write control unit for writing the write data read from the disk cache, and the same data is written to the two magnetic disk devices by one write command from the central processing unit. A magnetic disk control device characterized by the above.