JPH05120136A - Disk cache device - Google Patents

Abstract

PURPOSE:To increase the memory access speed and to improve the system performance by inserting a disk cache device between a host device and a fixed disk device. CONSTITUTION:A data transfer control part 7 controls the transfer of data between a host device 1 and a fixed disk device 2, between the host device 1 and a disk cache device 3 itself, and also between both devices 2 and 3 respectively. At the same time, a cache memory control part 8 writes and reads the data into and out of a cache memory 4. Therefore the disk cache device 3 retrieves the contents stored in the cache memory 4 by the access request given from the host device 1. Then the disk cache device 3 reads the requested data out of the cache memory 4 if stored. If not, the data is read out of the fixed disk device 2. In such a constitution, it is just required to apply the processing procedure similar to that of the fixed disk device 2 to the host device 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SCS of a host device.
The present invention relates to a disk cache device connected between an I interface and a SCSI interface of a fixed disk device.

[0002]

2. Description of the Related Art Generally, a host device 1 as shown in FIG.
In the SCSI type fixed disk device 2 used by connecting to the system, the frequency of use becomes high after introduction of the system, and it is often necessary to improve the performance of the current system. In this case, it is widely known that the performance can be improved by adding a disk cache device.

[0003]

However, when a fixed disk device 2 which does not originally have a disk cache device is additionally equipped with a new disk cache device, an interface for the disk cache device is added, It is necessary to add a transfer control device for switching the data transfer path among the host device 1, the fixed disk device 2, and the disk cache device, and also to change various command processes. However, it is practically impossible to retrofit the fixed disk unit because of the large amount of changes to the existing equipment unless the specifications for installing the disk cache unit from the beginning of the design. There was a problem.

The present invention has been made in view of the above-mentioned problems of the prior art. The fixed disk device which originally does not support the retrofitting of the disk cache device is modified into a host device and a fixed disk device. It is an object of the present invention to provide a disk cache device which can be additionally equipped without performing the above to speed up memory access and improve system performance.

[0005]

SUMMARY OF THE INVENTION In a disk cache device for buffering a difference in access speed between a main memory and a fixed disk device, the present invention provides a SCSI interface for connecting a host device having a target function and an initiator function. A fixed disk device connection SCSI interface, a transfer controller that switches between data transfer from the cache memory and data transfer from the fixed disk device when transferring data to the host device, and write and read data to and from the cache memory. And a cache memory control unit for controlling.

[0006]

In the disk cache device of the present invention, the SCSI interface having the target function is connected to the host device side, and the SCSI interface having the initiator function is connected to the fixed disk device side. As a result, by operating the SCSI interface on the side connected to the host device as a target and operating in the same manner as the fixed disk device, various processes are executed from the host device assuming that the fixed disk device is connected as usual. , S on the side to which the fixed disk device is connected
By operating the CSI interface as an initiator in the same manner as the host device, the fixed disk device can be operated as if it were connected to the host device as in the conventional case.

Therefore, the transfer control unit causes the cache memory to be simultaneously accessed in response to the access from the host device to the fixed disk device, and if there is a cache hit, transfers the data from the cache memory to the host device, If there is no cache hit, data is transferred from the fixed disk device to the host device in response to the access, and the access from the host device is speeded up.

[0008]

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

FIG. 1 shows a system configuration of an embodiment of the present invention. A disk cache device 3 of an embodiment of the present invention inserted and connected between a host device 1 and a SCSI type fixed disk device 2. Is the cache memory 4
And a host device 1 as an initiator, a SCSI interface 5 for connecting a host device having its target function, and an S for connecting a fixed disk device 2 having a fixed disk device 2 as a target and having an initiator function.
And a CSI interface 6.

A data transfer control unit 7 for controlling data transfer from the host device 1 to the fixed disk device 2, and conversely, data transfer from the fixed disk device 2 to the host device 1, and writing of data to the cache memory 4. Cache memory control unit 8 for controlling reading
Is equipped with.

Next, the operation of the disk cache device having the above configuration will be described.

By operating the SCSI interface on the side connected to the host device 1 as a target in the same manner as the fixed disk device 2, the fixed disk device 2 is directly connected to the host device 1 as in the conventional case. In addition, various processes such as data input / output command and data transfer are executed from the host device 1.

Further, similarly to the side to which the fixed disk device 2 is connected, this fixed disk device 2 is also conventionally used.
, The disk cache device 3 side is regarded as an initiator, and various processes such as data input / output command and data transfer are performed.

Data transfer between the host device 1 and the fixed disk device 2, data transfer between the host device 1 and the disk cache device 3 itself, and between the fixed disk device 2 and the disk cache device 3 itself. Is performed by the data transfer control unit 7. The cache memory control unit 8 writes and reads data to and from the cache memory 4.

Therefore, when the disk cache device 3 searches the contents stored in the cache memory 4 in response to the access request from the host device 1 and the requested data exists in the cache memory 4, The data is read from the cache memory 4, and if it does not exist, the data is read from the fixed disk device 2, and the data transfer is performed by the same process as the process for the conventional fixed disk device 2 as viewed from the host device 1.

The specific operation of the disk cache device will be described in more detail with reference to the flowchart of FIG. 2. When the host device 1 issues a seek request to the disk cache device 3 (step S).
1), the disk cache device 3 is a fixed disk device 2
A seek request is issued to (step S2).

Then, the disk cache device 3 does not wait for the seek of the fixed disk device 2 to be completed, but to the host device 1
A seek completion notification is issued to the
3). Therefore, the host device 1 issues a data transfer request to the disk cache device 3 (step S).
4). In response to this, the disk cache device 3 searches the contents stored in the cache memory 4 and checks whether there is a cache hit or a cache mishit (step S6).

If there is a cache hit in step S6, the corresponding data is stored in the cache memory 4
The data is read from the host computer and data is transferred to and from the host device 1 (step S7). In this case, the access time of the fixed disk device 2 is not necessary, and the access time overhead is shortened.

In step S6, if there is a cache miss hit, the completion of the seek of the fixed disk device 2 is waited for (step S8), and when the seek of the fixed disk device 2 is completed, the disk cache device 3 determines the fixed disk. A data transfer request is issued to the device 2 (step S9), and then the disk cache device 3 controls data transfer between the fixed disk device 2 and the host device 1 (step S10). If the data transfer at this time is reading of data from the fixed disk device 2, the read data is also stored in the cache memory 4 at the same time. In this case, since the access time of the fixed disk device 2 is required, the same overhead as that of the conventional system shown in FIG. 3, which is not equipped with the disk cache device, is required, but it is slower than that. Absent.

[0020]

As described above, the disk cache device of the present invention has a SCSI interface for connecting a host device having a target function, a SCSI interface for connecting a fixed disk device having an initiator function, and a data transfer for a host device. At this time, since the transfer control unit for switching the data transfer from the cache memory and the data transfer from the fixed disk device is provided, it is fixed to the host device by simply inserting and connecting it between the host device and the fixed disk device. The disk cache function can be realized simply by executing the same processing procedure as the disk device, and the performance of the fixed disk device can be easily improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the disk cache device of the above embodiment.

FIG. 3 is a block diagram showing a system configuration of a conventional example.

[Explanation of symbols]

1 Host Device 2 Fixed Disk Device 3 Disk Cache Device 4 Cache Memory 5 SCSI Interface with Target Function 6 SCSI Interface with Initiator Function 7 Data Transfer Controller 8 Cache Memory Controller

Claims (1)

[Claims] 1. A disk cache device for buffering a difference in access speed between a main memory and a fixed disk device, wherein a SCSI interface for connecting a host device having a target function and a fixed disk device for connecting a fixed disk device having an initiator function are provided. A SCSI interface, a transfer control unit that switches between data transfer from the cache memory and data transfer from the fixed disk device when transferring data to the host device, and a cache memory control unit that controls writing and reading of data to and from the cache memory. A disk cache device provided.