JPH0630076B2 - Disk cache device - Google Patents

Description

The present invention relates to a disk cache device, and more particularly to a disk cache device having a store-in function.

[Conventional technology]

In general, the interface signal line connecting the devices is set so that the lower device receives a reset instruction from the upper device when the power of the upper device is cut off or momentarily cuts off. There may be a reset instruction.

When the reset instruction is issued from the central processing unit during the write operation for the above reason, the data block in the write operation becomes indefinite. Since such an indefinite data block occurs due to the failure of the central processing unit,
It is expected that the recovery processing of an indefinite data block will be quite difficult, and it is quite possible to read this indefinite data block after the failure recovery of the host device.

In such a magnetic disk controller that uses a conventional magnetic disk device as a recording medium, at such a time, the write operation to the magnetic disk device is immediately interrupted. Normally, a data block stored on a magnetic disk device is composed of a sync byte for detecting the end of the data block, data, and an error detection / correction code, and at least the error detection / correction is caused by interruption of the write operation. Since the code is erased from the medium, an attempt to read such a data block could cause a read error and make the reading impossible.

[Problems to be solved by the invention]

In recent years, a disk cache device that reduces the difference between the processing speed of a central processing unit and the access speed of a magnetic disk device and improves system performance has been put into practical use, and one of the disk cache operations is a store-in operation. This conventional store-in operation updates only the data in the cache memory without the write operation to the magnetic disk device, so even if a failure occurs during the write operation in the cache memory, the write data will be It was impossible to detect indefinite data blocks on the included cache memory.

[Means for solving problems]

The disk cache device of the present invention has a plurality of data buffers provided between it and the central processing unit of the magnetic disk device, and means for transferring request data from the data buffer in response to a read request from the central processing unit. Means for performing a store-in operation of transferring write data to a data buffer in response to a write request from the central processing unit,
Reset latch means for latching a reset instruction from the central processing unit; means for setting a data indefinite flag added to write data when the reset latch is set during the store-in operation and writing the data in the data buffer; Means for resetting the data indefinite flag added to the write data and writing it in the data buffer when the reset latch is not set during the store-in operation; and data for which the central processing unit sets the data indefinite flag. And a means for reporting to the central processing unit that the read data is indefinite when reading data.

〔Example〕

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

FIG. 1 is a block diagram of an embodiment of the present invention, in which a disk cache device 10 is an MPU (microprocessor).
1, a cache memory 5, a cache adapter 4, a host adapter 2 having a reset latch 3 for latching a reset instruction from the host processor 30, and a disk adapter 6.

A host processor 30 is provided as a host device and is interconnected with the host adapter 2. The magnetic disk device 20 is interconnected with the disk adapter 6.

The cache memory 5 is a semiconductor memory having a series of address spaces, and Y data buffers are logically allocated in the cache memory 5.

FIG. 2 is a diagram of a track image of the magnetic disk device 20 adopting the CKD recording format. A home address field (HA), a count field (CF), a key field (KF), and a data field (DF) are arranged on the track, and an error detection / correction code for detecting and correcting a read error is provided in each field. In addition, there is a gap at the boundary of each field for continuously processing information on the magnetic disk medium which is constantly rotating.

FIG. 3 is a diagram of an image of a data buffer on the cache memory 5. Since the cache memory 5 is composed of a semiconductor memory, the gap on the magnetic disk 20 and the error detection / correction code are removed, and the data indefinite flag is coded for each field.

In response to a search or read instruction from the host processor 30 before all of the information on the target disk track is stored in the data buffer, the MPU 1 operates the magnetic disk device 20 and at the same time stores the third information in the data buffer.
Information is stored in the format shown in the figure. At this time, the data indefinite flag of each field is reset.

The MPU 1 does not write the information sent from the host processor 30 to the magnetic disk device 20 in response to the subsequent write instruction from the host processor 30 which is stored in all the data buffers of the information on the target disk track.
Write to specified field of data buffer (store-in operation). The MPU 1 resets the data indefinite flag when the reset latch 3 is not set until the data transfer from the host processor 30 is completed, and sets the data indefinite flag when the reset latch 3 is set.

Next, in response to a search and read instruction from the host processor 30 after all the information on the target disk track is stored in the data buffer, the MPU 1 reads the designated field in the data buffer and searches. In the case of an instruction, it is compared with the data sent from the host processor 30, and in the case of a read instruction, the host processor 3
Data is transferred to 0. At this time, the data indefinite flag of the designated field is checked, and if this is set, it reports that the data of the field accessed to the host processor 30 is indefinite.

[Effects of the Invention] As described above, by using the disk cache device of the present invention, it is possible to store indefinite data in the cache memory, and the indefinite data is erroneously transferred to the central processing unit. The effect that the reliability of the information processing system can be improved and the field that has become indefinite in the cache memory is instructed to write again from the central processing unit, and this write operation ends normally. Since it is possible to recover by this, there is an effect that a recovery process for a conventional magnetic disk device can be easily applied to this indefinite data as a recovery process performed by the central processing unit.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a track image of a magnetic disk device, and FIG. 3 is a diagram of a data buffer. 1 ... MPU (microprocessor), 2 ... Host adapter, 3 ... Reset latch, 4 ... Cache adapter, 5
... cache memory, 6 ... disk adapter, 10 ... disk cache device, 20 ... host processor (central processing unit), 30 ... magnetic disk device.

Claims (1)

[Claims] 1. A means for transferring request data from a data buffer to a read request from the central processing unit, the central processing unit having a plurality of data buffers provided between the magnetic disk unit and the central processing unit. A means for performing a store-in operation for transferring write data to a data buffer in response to a write request from the device, a reset latch means for latching a reset instruction from the central processing unit, and a reset latch set during the store-in operation. Means for setting the data indefinite flag added to the write data when the data is written to the data buffer, and the data indefinite flag added to the write data when the reset latch is not set during the store-in operation Means for resetting and writing in the data buffer, and the central processing unit Disk cache device, characterized in that it comprises a means for reporting to the central processing unit that read data is indefinite when reading data set the serial data indeterminate flag.