JPH0934654A - Disk array subsystem - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the disk array subsystem which improves the write performance by reducing the storage read area at the time of storage write. SOLUTION: A disk array subsystem 10 is provided with a disk control part 20 and a disk device part 30, and the disk device part 30 is provided with N disk drives 311 to 31N, and the disk control part 20 is provided with disk device control parts 201 to 20N, a disk array control part 210, and a storage area releape mechanism 220. A redundant storage area is provided in the storage area on the disk drive, and a storage area operation table is stored in another storage area on the redundant storage area or on the same disk annexed to the redundant storage area, and information indicating whether data on the storage area is valid or not is stored in the storage area operation table.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk array subsystem used in a general computer system, and more particularly to a disk array device and a disk array control device having equivalent functions when regarded as one.

[0002]

2. Description of the Related Art A disk array device or a disk array subsystem is superior to a single disk in terms of price-performance ratio, reliability, etc., and is widely used in fields requiring high performance and high reliability. ing. There are various types of disk arrays, but the mainstream currently is "RAI
This is a construction method called “D5”.

In a general disk subsystem, a storage area on a disk drive is read and written in units called "records".

In RAID 5, one of a plurality (= N) of disk drives is assigned to a redundant storage area called "parity". There is one parity record for each corresponding record on the (N-1) disk drives.

The contents of the parity record are the corresponding N-
It is given by the parity of the data of one record, that is, the exclusive logical product or the exclusive logical sum.

Therefore, even if a failure occurs in one disk drive, the exclusive logical product or exclusive OR of all the other drives is obtained to reproduce the data on the failed disk drive. It becomes possible to do.

However, although the parity is added in record units, since the parity record itself is distributed in N disk drives, which disk drive stores the parity depends on the configuration of the subsystem.

The subsystem having the RAID 5 configuration is characterized in that a plurality of read (read) requests and write (write) requests from a higher-level device can be simultaneously performed as long as the processing to the same drive is not duplicated.

At this time, the read operation is the same as the processing by a single drive, but the write operation is performed by the R drive.
Processing specific to AID5 is required.

That is, in RAID 5, when writing data, the parity record must be updated to compensate the parity on the corresponding record.

The parity record is updated according to the following procedure (steps 0 to 4).

(0) A data write command is received from the host device.

(1) A read (also called "read") process is performed on a record to be written.

(2) Read processing is performed on the parity record to be updated.

(3-1) Write the write data in a predetermined record.

(3-2) Data of the parity record to be updated is generated from the data of the above record.

(4) Write and update parity data.

The above step (3-2) is an operation in the disk array control section, but all the other steps require reading or writing of the disk drive.

[0019]

In the above-described conventional example, in order to write data to one record,
As described above, reading and writing to the disk drive must be performed four times in total.

This means that processing overhead is generated as compared with the case of a single disk.

For this reason, conventionally, virtual memory such as cache memory is used to read / write data to / from a disk drive.
Methods have been proposed to minimize writing. However, cache memory (also called disk cache)
In a system using virtual memory such as, it is not always necessary to read / write the disk drive, and the operation is different.

However, a method of suppressing the number of times of reading / writing on the disk drive itself has not been sufficiently studied.

Therefore, an object of the present invention is to provide a disk array subsystem capable of suppressing the number of input / output times (read / write times) with respect to a disk drive.

[0024]

To achieve the above object, the present invention provides a plurality of (= N) disk drives,
A disk control unit that controls the plurality of disk drives, and secures a storage area for at least one of the plurality of disk drives as a redundant storage area,
Using the redundant storage area, means for compensating data when one of the plurality of disk drives fails, and the same disk drive on or associated with the redundant storage area The upper storage area has an area for storing information indicating whether or not the data in the storage area on another disk drive corresponding to the redundant storage area is valid. A means for releasing the storage area on the drive is provided, and whether or not the data in the storage area on another disk drive corresponding to the redundant storage area on the redundant storage area is valid as the storage area is released There is provided a disk array subsystem characterized by having a means for updating an area for storing information indicating that or not, and also for updating a redundant storage area itself. It is a disk array subsystem with a passive storage release mechanism.

Further, the present invention comprises a plurality (= N) of disk drives and a disk control unit for controlling the plurality of disk drives, and stores at least one of the plurality of disk drives. An area is secured as a redundant storage area, and means for compensating data when a failure occurs in one of the plurality of disk drives using the redundant storage area is provided on the redundant storage area or on the redundant storage area. On the storage area on the same disk drive accompanying the storage area, there is an area for storing information indicating whether or not the data in the storage area on another disk drive corresponding to the redundant storage area is valid, The storage area release condition determination means provided in the control means of the disk subsystem and the storage area on the disk drive that is activated by the storage area release condition determination means A means for releasing the storage area, and when the storage area is released, information indicating whether or not the data in the storage area on another disk drive corresponding to the redundant storage area on the redundant storage area is valid is displayed. There is provided a disk array subsystem having means for updating a storage area and at the same time updating the redundant storage area itself. This is a disk array subsystem with an active storage release mechanism.

[0026]

In the present invention, the predetermined storage area is provided in the redundant storage area, that is, in the parity record or in another record on the same disk attached to the parity record. This storage area is called a "storage area operation table".

The storage area operation table indicates whether or not the record of another disk drive, which literally corresponds to the parity record, holds valid data.

For the data on the parity record, the parity is generated only from the record which is shown to be valid on the storage area operation table. A record that is invalid in the storage area operation table is irrelevant to the parity record.

Although the storage area operation table is added to the parity record, an area having the same capacity as the storage area operation table is added to records other than the parity record. This is called a "storage area operation table compensation area".

Further, in the present invention, the storage area on the disk drive is released due to a command from the host device or a physical or logical condition in the subsystem, that is, "valid" on the storage area operation table. It has a mechanism for switching the display of "" to "invalid". However, the parity record needs to be updated even when the storage area is released.

According to the present invention, the number of read / write operations of the disk drive when updating the parity record is reduced by using the above-mentioned storage area operation table.

In the above-mentioned conventional example, it was necessary to read and write the disk drive four times when updating the parity record.

In the present invention, the parity record is updated in the following procedure.

(0) Receive a data write command from the host device.

(1-1) Read (read) processing is performed on the data of the parity record. At the same time, the storage area operation table is also read.

(1-2) When the data is written in the unused area from the storage area operation table, the process proceeds to step (3-1).

(2) Read processing is performed on the record updated by writing data.

(3-1) The updated value of the parity record is generated from the value of the above record.

(3-2) Write the write data in a predetermined record. At this time, the updated value of the storage area operation table compensation area is also written.

(4) Write and update parity data. At this time, the storage area operation table is also updated.

That is, in the present invention, when writing to an unused area of the storage area (because step 2 is omitted), it is possible to reduce the number of read / write operations of the disk drive to three.

[0042]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, a disk array subsystem including five disk drives is assumed.

FIG. 2 is a diagram showing the overall configuration of the disk array subsystem according to this embodiment.

Referring to FIG. 2, the disk array subsystem 10 includes a disk control unit 20 and a disk device unit 30.
It is composed of

The disk device section 30 includes five disk drives 311 to 315.

The disk controller 20 includes disk device controllers 201 to 205 corresponding to the disk drives 311 to 315, and the disk array controller 210.
And a storage area release mechanism 220 for controlling the release of the storage area. The disk control unit 20 can independently control the disk drives 301 to 305.

FIG. 3 shows the state of the storage area on the disk drive.

Records 3110 on the disk drive
Parity records 31X0, 31X1, ... Are provided in 3150, 3111 to 1511, ..., And storage area operation tables 31Y0, 31 are stored in another storage area on the parity record or on the same disk attached to the parity record.
Y1, ... Is stored.

FIG. 4 is a diagram for explaining the structure and contents of the storage area operation table.

The storage area operation table 31Y0 contains the record 31
The usage statuses of 10 to 3150 are expressed by three numerical values.

"0" indicates that the corresponding record is unused. “1” indicates that the data of the corresponding record is valid. “2” indicates that the corresponding record is a parity record.

FIG. 5 and FIG. 6 are flowcharts for explaining the processing at the time of writing data in this embodiment. In FIGS. 5 and 6, the write data is (N), the data of the record before being written is (O),
The data of the parity record is represented by (P). Note that, in FIGS. 5 and 6, the reference numerals in parentheses attached to the respective steps indicate that they correspond to the step at the time of writing, which has been described in the above-mentioned "action" column.

First, the parity record is read (step 501). At that time, the storage area operation table is also read at the same time.

When the record is unused by referring to the storage area operation table (step 502), when all the records corresponding to the parity record are unused, it is being used for the storage area operation table compensation area. And a value indicating that it is parity (step 504), FIG.
Then, the process proceeds to step 605. If all the records are not unused, a value indicating that they are in use is written in the storage area operation table compensation area (step 505), and the process proceeds to step 604 in FIG.

Referring to FIG. 6, if all the records are unused, the parity of the write data (N) is generated (step 605), and if all the records are not unused, the data of the parity record ( The updated parity is obtained by the exclusive OR operation of P) and the write data (N) (step 604).

After obtaining the update parity, the record of the write data is written (step 606) and the parity record is also written (step 607).

If there is no unused record, the update record is read (step 601) and the storage area operation table compensation area is not changed (step 60).
2) The update parity is obtained by the exclusive OR operation of the data (P) of the parity record, the data (O) of the record before being written, and the write data (N) (step 603).

FIG. 1 is a diagram showing how the contents of a record change when writing data to an unused record in this embodiment. In the figure, record 31
X0 is assigned to the parity record. The storage area operation table 31X0 is provided at the beginning of the parity record 31X0.
1 is added. In the records 3110 to 3130 and 3150 other than the parity record, a storage area having the same capacity as the storage area operation table and a storage area operation table compensation area 31101 to
31301 and 31501 are secured. The storage area operation table compensation area is provided for compensating the parity of the storage area operation table, and the exclusive OR or exclusive logical product of the storage area operation table compensation area matches the storage area operation table. .

FIG. 1 shows the operation when writing to the record 3150 (corresponding to FIG. 3).

In FIG. 1A, the parity record 31X
Read 0. Here, from the storage area operation table 31X01 (the content of the storage area operation table is “11020”), record 3
The value of the area corresponding to 150 is “0”, and the record 3
It can be seen that 150 is unused.

In FIG. 1B, the data (“1234”) is written in the record 3150. At this time, in the storage area operation table compensation area 31501, only the area corresponding to the record 3150 is written with the value “1” indicating that it is in use (indicated by an arrow in FIG. 1B).

In FIG. 1C, the parity record 31X
Write to 0. The value written in the parity record 31X0 is the value read in the step shown in FIG.
AAA ": hexadecimal display) and the value of the record 3150 written in the step shown in FIG.
34 ") and the exclusive OR (" B89E ").

In the storage area operation table 31X01, the area corresponding to the record 3150 is rewritten as "1" (indicated by the arrow in FIG. 1C).

By writing the value "1" indicating that the storage area operation table is in use in the storage area operation table compensation area in FIG. 1B, the entire parity record including the storage area operation table is in use. It is expressed as the exclusive OR of a certain record.

FIG. 7 is a diagram showing changes in the contents of records when all the records are unused, as a special case when writing data to unused records in the embodiment of the present invention.

In FIG. 7, record 3110 (see FIG. 3)
The operation of writing to is shown.

In FIG. 7A, the parity record 31X
Read 0. Here, the storage area operation table 31X01 (“0
From 0020 ″), it can be seen that the value corresponding to the record 3110 is “0” and the record 3110 is unused.

In FIG. 7B, data (“3333” in this case) is written in the record 3110. At this time, the record 3110 is stored in the storage area operation table compensation area 31101.
A value of "1" indicating that it is being used is written in the area corresponding to the
A value of "2" indicating that it is a parity record is written ("1002" in the storage area operation table compensation area 31101).
It becomes 0 ").

In FIG. 7C, the parity record 31X
Write to 0. The value to be written is (B) and is record 3110.
It is the same as the value written in. Storage area operation table 31X0
1 rewrites the area corresponding to the record 3110 as “1”.

In the write operation when all the records are unused, the write data for the parity record is the same as the write data for the normal record, which is different from the case where there is a record in use. Also, in writing the status of the parity record in the storage area operation table compensation area of the normal write record,
This differs from the case where there are records in use.

FIG. 8 is a flow chart for explaining the processing flow for releasing the storage area.

In the case of passive release of the storage area, as a command from the host device, there may be a normal command such as deletion of a file or a record in addition to a special command for releasing the storage area.

In the case of actively releasing the storage area, there may be a case where the record data is read to the cache memory or the non-volatile memory inside the disk array subsystem.

Referring to FIG. 8, a parity record is read (step 801), and when the record is in an unused state by referring to the storage area operation table (judgment in step 802), it corresponds to the parity record. If all records are unused (release all records),
Only the storage area operation table is updated (step 806). When all the records are not unused, the released record is read (step 804), the parity is updated from the read record (F) and the parity record (P) (step 805), and the parity data is written to the parity record (step). 807). If the record is in use in the determination of step 802, the storage area operation table is updated (step 806) and the parity data is written.

FIG. 9 is a diagram showing how the contents of a record change when the storage area is released in this embodiment.

As shown in FIG. 9A, the parity record 31X0 (indicated by an arrow in the figure; see also FIG. 3) is read. Here, it can be seen from the storage area operation table 31X01 that the record 3150 is in use.

In FIG. 9B, the data (“1234”) of the record 3150 is read.

In FIG. 9C, the parity data is written in the parity record 31X0. The value to be written is shown in Figure 9.
The value read in the step shown in (A) ("B89
E ”) and the value (“ 1234 ”) of the record 3150 read in the step shown in FIG. 9B is the exclusive OR (“ AAAA ”).

The storage area operation table 31X01 has record 3
The area corresponding to 150 is rewritten as "0", which is an unused meaning.

FIG. 10 is a diagram showing how the contents of the records change when releasing all the records corresponding to one parity record as a special case when releasing the storage area.

Referring to FIG. 10, no record is read and only the storage area operation table of the parity record (indicated by an arrow in the figure) is rewritten.

FIG. 11 illustrates how the contents of a record change when data is reconstructed on a replacement disk drive or a new disk drive that has been replaced when a failure occurs in one disk drive. It is a thing. In FIG. 11, the disk drive 311 (see FIG. 2)
Above is shown the case of reconstructing the data.

In FIG. 11A, the parity record 31
X0 (indicated by an arrow in the drawing, with reference to FIG. 3, the records are 3110, 3120, 3130, 31X from the left end side).
0, 3150) is read. Storage area operation table 31
It can be seen from 410 that the records 3110, 3120, and 3150 hold valid data (records whose storage area operation table value corresponds to “1”).

In FIG. 11B, the record 3110 is read. Also, the record 3150 is read. These can operate simultaneously.

In FIG. 11C, the reconstructed data is written in the record 3110 (indicated by the arrow in the figure). The reconstructed data is given by the exclusive OR of the records 3110 and 3150 and the parity record 31X0.

In this embodiment, the record 3120
Characteristically, there is no need to read.

FIG. 12 shows a special case of reconstructing data on an alternative disk drive or a new disk drive which has been replaced when a failure occurs in one disk drive. It is a figure showing change of the contents of a record at the time of construction. FIG.
2 shows a case where data is reconstructed on the disk drive 311 (see FIG. 2).

In FIG. 12, although the parity record 31X0 is read, the reconstruction process is not performed because the record 3130 is unused, that is, the record 3130.
Indicates that nothing was written to.

As described above, according to the embodiment of the present invention, it is possible to reduce the number of times of reading and writing to the disk drive during the data writing process to the disk array subsystem from the conventional four times to three times. In addition, the active or passive storage area release mechanism can reduce the number of times data is read and written even when reconstructing data.

However, in this embodiment, it cannot always be said that the performance of the disk array subsystem is immediately improved. This is because the number of times of reading / writing from / to the disk drive at the time of writing data is reduced, but the reading / writing of the disk drive is also required at the time of releasing the storage area.

Considering the case where the freeing of the storage area and the writing to the unused area are performed on a one-to-one basis, a total of 6 readings and writings to the disk drive are required.

Considering that the number of times of reading / writing of the disk drive at the time of writing in the normal disk array subsystem is 4, it can be said that the performance is deteriorated.

However, considering that a large-capacity cache memory or a non-volatile memory is indispensable in a disk array subsystem today, the embodiment of the present invention cannot be considered to cause performance degradation.

This is because four of the six readings and writings are for the parity record, and as a result, the cache hit rate of the parity record is improved. Increasing the cache hit rate simply contributes to improving the performance of the disk array subsystem. Although the embodiment of the present invention is independent of the presence or absence of the cache memory, it is certainly possible to improve the performance by adding the cache memory.

As described above, according to this embodiment, the writing process can be performed faster than the conventional disk array subsystem, and the unused area on the disk drive can be increased even during operation. Is.

[0096]

As described above, according to the present invention,
This has the effect of reducing the number of times of reading and writing to the disk drive during the data writing process to the disk array subsystem from the conventional four times to three times.

Further, according to the present invention, it is possible to increase the unused area on the disk drive even during operation by the active or passive storage area releasing mechanism. Further, it is possible to reduce the number of times of reading and writing data even when reconstructing data.

Further, as described above, it may not always be said that the performance of the disk array subsystem is immediately improved by adopting the present invention. However, today, in the disk array subsystem, a large capacity cache is provided. Considering that the memory or the non-volatile memory is indispensable, the present invention is not considered to cause performance degradation. This is because, of the 6 times of reading and writing, 4 times are for the parity record, as a result, the cache hit rate of the parity record is improved, and the increase of the cache hit rate simply contributes to the performance improvement of the disk array subsystem. That is, the present invention is independent of the presence or absence of the cache memory, but it is certainly possible to improve the performance by adding the cache memory.

The present invention makes it possible to perform the writing process at a higher speed than the conventional disk array subsystem.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an example of how a record is updated when writing data in an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a disk array subsystem according to an embodiment of the present invention.

FIG. 3 is a diagram schematically showing a data record in each disk drive of the disk array subsystem according to the embodiment of the present invention.

FIG. 4 is a diagram for explaining a storage area operation table and its structure according to an embodiment of the present invention.

FIG. 5 is a flowchart for explaining a write processing operation in the disk array subsystem according to the embodiment of the present invention.

FIG. 6 is a flowchart for explaining a write processing operation in the disk array subsystem according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating a case where all corresponding records are unused as a special case at the time of writing data in the embodiment of the present invention.

FIG. 8 is a flowchart illustrating a processing flow for releasing a storage area according to the embodiment of the present invention.

FIG. 9 is a diagram showing how records are updated when a storage area is released in an embodiment of the present invention.

FIG. 10 is a diagram showing a case where all corresponding records are made unused as a special case of storage area release according to an embodiment of the present invention.

FIG. 11 is a diagram showing how records are updated when data is reconstructed in the embodiment of the present invention.

FIG. 12 is a diagram showing a case where a record to be reconstructed is unused as a special case of data reconstruction in an embodiment of the present invention.

[Explanation of symbols]

 10 disk array subsystem 20 disk control unit 30 disk device 210 disk array control unit 220 storage area release mechanism 201 to 205 disk device control unit 311 to 315 disk drive

Claims (4)

[Claims] 1. A plurality of (= N) disk drives, and a disk control unit for controlling the plurality of disk drives,
A storage area for at least one of the plurality of disk drives is secured as a redundant storage area, and one of the plurality of disk drives is used by using the redundant storage area.
When a failure occurs in the table, a means for compensating data is provided, and another disk drive corresponding to the redundant storage area is provided on the redundant storage area or a storage area on the same disk drive attached to the redundant storage area. It has an area for storing information indicating whether or not the data in the upper storage area is valid, and is provided with means for releasing the storage area on the disk drive in response to a command from the host device. , Updating an area for storing information indicating whether or not data in a storage area on another disk drive corresponding to the redundant storage area, which is on the redundant storage area, is valid, and also updates the redundant storage area itself. A disk array subsystem comprising: 2. A plurality of (= N) disk drives, and a disk control unit for controlling the plurality of disk drives,
A storage area for at least one of the plurality of disk drives is secured as a redundant storage area, and one of the plurality of disk drives is used by using the redundant storage area.
A means for compensating for data when a stand fails, on the redundant storage area or on a storage area on the same disk drive attached to the redundant storage area, on another disk drive corresponding to the redundant storage area Storage area release condition determination means provided in the control means of the disk subsystem, and the storage area release condition determination means, which is activated by the storage area release condition determination means. And has a means for releasing the storage area on the disk drive. With the release of the storage area, the data in the storage area on another disk drive corresponding to the redundant storage area on the redundant storage area is valid. Disk array sub, characterized in that it has means for updating an area for storing information indicating whether or not Stem. 3. A plurality of (= N) disk drives, and a disk control unit for controlling the plurality of disk drives,
A storage area for at least one of the plurality of disk drives is secured as a redundant storage area, and one of the plurality of disk drives is used by using the redundant storage area.
When a failure occurs in the table, a means for compensating data is provided, and another disk drive corresponding to the redundant storage area is provided on the redundant storage area or a storage area on the same disk drive attached to the redundant storage area. It has an area that stores information that indicates whether the data in the upper storage area is valid, and is activated by a command from a higher-level device or by the storage area release condition determination means provided in the control means of the disk subsystem. And a means for releasing the storage area on the disk drive is provided. With the release of the storage area, the data in the storage area on another disk drive corresponding to the redundant storage area on the redundant storage area becomes valid. A disk array sub characterized by having means for updating an area for storing information indicating whether or not there is, and at the same time updating the redundant storage area itself. system. 4. A plurality of (= N) disk drives, and a disk control unit for controlling the plurality of disk drives,
At least one of the plurality of disk drives includes a storage area operation table that stores the operation status of a corresponding storage area of another disk drive in a predetermined storage area, and a redundant storage area when writing data. Read the data and the storage area operation table, and when the writing of data from the storage area operation table is writing to an unused storage area, the update value of the redundant storage area is generated from the value of the write data. A disk array subsystem configured to write the write data in a predetermined record, write the update value in the redundant storage area, and update the storage area operation table.