JPH02109151A - Disk cache control system - Google Patents

Abstract

PURPOSE:To process a defective sector at a high speed by using a BB (battery back-up) RAM to secure area in the BBRAM for the defective sector and attaining the cache control even to a write request. CONSTITUTION:A control part 5 receives a data write request from a host computer 1 via a host interface 2 and retrieves a disk address storing part 6 of a BBRAM 3 to search an area where a flag is set at 1, 2 or 3 and the same time an address equal to that contained in the write request is stored. Then the part 5 replaces the data stored in an area corresponding to a data storing part 8 with the data contained in the write request. If the address is not searched, a flag storing part 7 is retrieved to search can area where the flag is set at 0 or 1. Thus the data required by the write request is written into an area corresponding to the part 8. Then the address of the written data is written into an area corresponding to the part 6. Then the flag is set at 2 and the end of a task is reported to the interface 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a disk cache control method for performing cache control in a disk device connected to a small computer or the like.

[Conventional technology]

The disk device must be equipped with a RAM for cache control, and when there is a read request from the host computer, if the desired data is held in the RAM, that data must be transferred to the host computer and held there. For example, it has been conventional practice to read target data from a disk, store it in a RAM, and then transfer it to a host computer. Additionally, if there is a defective sector on the disk that cannot be used to write data, it has been conventional practice to write data to an alternative sector on the disk and then use that alternative sector to read and write data. It is.

[Problem to be solved by the invention]

As mentioned above, by using the RAM for cache control, it is possible to speed up data reading from the disk device, but when the power to the disk device is turned off, the storage contents of the RAM for cache control are lost. Conventionally, data is written directly to the disk without performing cache control for write requests. For this reason, there was a problem in that it was not possible to speed up the writing of data to the disk device. Furthermore, as mentioned above, conventionally, when a defective sector exists on a disk, data is read and written using an alternative sector on the disk, and write requests and read requests to the defective sector are If there was, the defective sector had to be accessed first to find out the location of the replacement sector, and then the replacement sector had to be accessed.
There is a problem in that when there is a write request or read request to a defective sector, an extra seek operation is required.

An object of the present invention is to enable cache control even for write requests and to speed up processing when a write request or read request is made to a defective sector.

[Means to solve the problem]

In order to achieve the above object, the present invention includes: a disk, a battery backup RAM, and a disk and a battery backup RAM according to a read request and a write request from a host computer.
control means for controlling M, and the control means, in response to a read request from the host computer,
If the data at the location on the disk specified by the location information included in the cough read request is held in the pantry backup RAM, the data is transferred from the pantry backup RAM to the host computer, and if the data is not held. If not, read data stored in a location specified by the location information included in the read request from the disk, write it together with the location information in the battery backup RAM, and transfer the read data to the host computer; In response to a write request from the host computer, if the data at the location on the disk specified by the location information included in the write request is held in the battery backup RAM, the data requested by the write request is replacing the corresponding data held in the battery backup RAM, and if the data is not held, writing the data requested by the write request and the position information included in the write request in the battery backup RAM; During a period when there is no write request or read request from the host computer, the data written to the battery back amplifier RAM according to the write request is written to the disk according to the position information, and if data writing fails, the data is written to the battery back amplifier RAM. The area in which the above writing failed data is stored is set as a replacement area for the area on the disk where data writing failed, and data writing to the replacement area by a write request to another area is prohibited.

[For production]

When there is a read request from the host computer, if the target data, that is, the data at the position on the disk specified by the position information included in the read request, is held in the battery backup RAM, the control means Transfer the target data from the battery backup RAM to the host computer. If the target data is not held, the control means reads the target data from the disk, stores it together with the position information in the battery backup RAM, and transfers it to the host convenience store.

When a write request is received from the host computer, if the data stored at the location on the disk specified by the location information included in the write request is held in the battery backup RAM, the control means issues a write request for the data. Replace with the data requested by. Also, the data at the location on the disk specified by the location information included in the write request is transferred to the battery backup RA.
If the data is not held in M, the control means transfers the data requested by the write request and the position information indicating the position on the disk where the data is to be written to the battery back amplifier RAM.
write to.

Further, the control means receives a write request 5 from the post computer.
The data written to the battery backup RAM according to the write request during a period when there is no read request is written to the disk according to the position information. At that time, the area of the battery bank amplifier RAM where the data that failed to write is stored is set as a substitute area for the area on the disk where data writing failed, and data is written to the substitute area by a write request to another area. prohibited.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, in which a host computer 1 that makes a data read or write request to the host interface 2, a battery backup RAM 3, a disk 4, and the host interface 2 It includes a control unit 5 that receives write and read requests from the host computer I and controls the battery backup RAM 3 and the disk 4.

FIG. 2 is a diagram showing an example of the configuration of the battery backup RAM 3, which has a data storage section 8 consisting of a plurality of areas in which data is stored, and areas corresponding to each area provided in the data storage section 8. The data storage unit 8 has a flag storage unit 7 in which a flag indicating the state of data stored in a corresponding area of the data storage unit 8 is stored, and an area corresponding to each area provided in the data storage unit 8. , and a disk address storage section 6 in which the address on the disk 4 of the data stored in the corresponding area is stored.

In this embodiment, the flags stored in the flag storage section 7 can take values from "0" to "3";
0” indicates that the data stored in the corresponding area of the data storage unit 8 is invalid data, “1” indicates that the data has been read from the disk 4, and “2” indicates that the data has not yet been written to the disk 4. The data has not yet been completed.
“3” indicates data that failed to be written to the disk 4. Further, a disk address storage section 6,
The number of areas provided in the flag storage section 7 and the data storage section 8 needs to be sufficiently larger than the number of defective sectors that may exist on the disk 4. Further, the contents of the flag storage section 7 are all set to rOJ at the time of initial setting.

Next, the operation of this embodiment will be explained with reference to each figure.

When the control unit 5 receives a data write request (including the data to be written and the disk address to write the data) output from the host computer 1 via the host interface 2, the control unit 5 stores the disk address in the battery bank amplifier RAM 3. Section 6 is searched and the flag value is rlJ,
Instead of searching for an area in r2J or r3J in which the same address as the address included in the write request is stored, the control unit 5 searches for an area in which the same address as the address included in the write request is stored. If it can be found, the data held in the corresponding area of the data storage section 8 is replaced with the data included in the write request, and if it cannot be found, the flag storage section 7 is searched and the stored data is replaced. One area is searched for where the value of the flag is rOJ or "1" (however, the area rOJ is given priority).

When the control unit 5 finds one area where the value of the flag is "0" or "1", it writes the data requested by the write request to the corresponding area of the data storage unit 8, and also stores the disk address. The disk address included in the write request is written in the corresponding area of the section 6, and when writing of the data and disk address is completed, the value of the flag stored in the above-mentioned searched area of the flag storage section 7 is set to "2". After that, the write completion report is notified to the host interface 2. This write completion report is notified to the host computer l via the host interface 2.

The control unit 5 also receives a data read request (
(including the disk address of the data that should not be read), the disk address storage section 6 and flag storage section 7 of the ASSOBU RAM 3 are searched, and the value of the flag stored in the flag storage section 7 is determined as rOJ. A search is made for one area in which the disk address ζ stored in the disk address storage unit 6 matches the disk address included in the read request. ” If an area satisfying the oral conditions is found, the control unit 5 reads the data stored in the corresponding area of the data storage unit 8 and transfers the read data to the post computer 1 via the post interface 2. do.

If it is not possible to find an area that satisfies the above conditions, the data corresponding to the disk address included in the read request is read from the disk 4, transferred to the host computer 1 via the boss interface 2, and the data The data and disk address are stored in the data storage section 8. Write to the area in the disk address storage unit 6 where the flag value is rOJ or rlJ (however, the area with "0" is given priority), and then set the flag value to "1".

Further, if a write or read request is not applied from the host computer 1 via the host interface 2, the control unit 5 searches the flag storage unit 7 of the panteribus associate RAM 3 and determines that the value of the stored flag is “ The data stored in the area of the data storage section 8 corresponding to the searched area is transferred to the disk 4 according to the disk address stored in the corresponding area of the disk address storage section 6. Write.

If the write is successful, set the flag value to "1".
If it fails, it will be set as "3". Here, in the area where the flag value is set to "3", data is not written by a write request whose disk address does not match, but is written only by a write or read request whose disk address matches.

Since reading is performed, this area becomes a replacement area for the area on the disk where data writing failed. In addition, disk addresses, flags, and data are stored in battery-backed RAM.
3, it will be retained even if the power to the disk device is turned off, and will remain valid the next time the power is turned on.

Therefore, even if the power is turned off before data writing to the disk 4 is completed, writing to the disk 4 will be performed the next time the power is turned on, so cache control is also performed for write requests. becomes possible.

〔Effect of the invention〕

As explained above, since the present invention uses the battery backup RAM, it is possible to perform cache control even in response to write requests.
Since it is placed on M, even if there is a read request or write request to a defective sector, there is no need to perform a wasteful shift operation as in the conventional example. Therefore, according to the present invention, it is possible to read and write data on a disk at high speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing an example of the configuration of a battery backup RAM. In the figure, °ζ, ■... host computer, 2...
Host interface, 3... Battery backup RAM, 4... Disk, 5... Control unit, 6...
Disk address storage section, 7...Flag storage section, 8.
...Data storage section.

Claims (1)

[Scope of Claims] A disk, a battery backup RAM, and the disk and the battery backup RAM according to a read request and a write request from a host computer.
control means for controlling M, and the control means, in response to a read request from the host computer,
If the data at the location on the disk specified by the location information included in the read request is held in the battery backup RAM, the data is transferred from the battery backup RAM to the host computer; if the data is not held, the data is transferred to the host computer; The data stored in the location specified by the location information included in the read request is read from the disk and written together with the location information in the battery backup RAM, the read data is transferred to the host computer, In response to a write request from the computer, if the data at the location on the disk specified by the location information included in the write request is held in the battery backup RAM, the data requested by the write request is used. replacing the corresponding data held in the battery backup RAM, and if the corresponding data is not held, writing the data requested by the write request and the position information included in the write request in the battery backup RAM; The data written to the battery backup RAM according to the write request during a period when there is no write request or read request from is written to the disk according to the position information, and if writing of data fails, writing on the battery backup RAM fails. The disk is characterized in that an area in which data is stored is used as a substitute area for the area on the disk where data writing has failed, and writing of data to the substitute area by a write request to another area is prohibited. Cache control method.