JP2001142653A - Disk subsystem having mirrored disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the throughput performance of data read by a pre-reading function for a mirrored disk in a disk subsystem having a mirrored disk device. SOLUTION: A disk device 12 is a mirrored disk device consisting of a data disk Di and a parity disk Pi. Each of devices constituting the device 12 is respectively connected to a disk controller 8 through a different loop 10-1 or 10-2. The controller 8 uses the data disk Di or the parity disk Pi so as to scatter the data transfer loads of the loops 10-1 and 10-2 about data read by the pre- reading function. When the data of D1-D2 and D3-D4 are respectively striped, the loads of the loops 10-1 and 10-2 are scattered by performing data read of the D1-D2 and P3-P4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk subsystem having a disk device according to the RAID 1 system (mirroring), and more particularly to a plurality of transmission lines connecting a disk controller and a mirrored disk device.
The present invention relates to a disk subsystem that controls to distribute the load on a transmission line due to data transfer between the two.

[0002]

2. Description of the Related Art A disk subsystem has a disk controller and a plurality of disk devices, and both are connected by a transmission line. A disk device adopting the RAID1 system is a device called a mirrored disk, and is composed of a data disk drive and a parity disk drive. The data drive and the parity drive are connected to the disk control device via different transmission paths.

FIG. 8 is a diagram showing a configuration example of a conventional disk subsystem. The disk subsystem includes a disk control device 7, a disk device 14, and loops 10-1 and 10-2 connecting the disk control device 7 and the disk device 14. The disk control device 7 is connected to the host computer of the host device. The disk device 14 is a mirrored disk device and includes a data disk Di and a parity disk Pi, and data is striped across the data disks D1 to D4. Therefore, parity disk P
The same data is striped from 1 to P4. Since the disk control device 7 has a cache memory, if the read-ahead function is used when reading data from the data disks D1 to D4 by sequential access, the data reading speed as viewed from the host computer is improved.

[0004]

According to the above-mentioned conventional disk subsystem, when data is read from the data disks D1 to D4 by the prefetch function, only the loop 10-1 is used. There is a problem that the loop 10-1 is occupied for the transfer and the load on the transmission line is offset. Therefore, each of the data disks D1 to D5
A data transfer amount bottleneck on the loop 10-1 side occurs compared to the data read performance of the loop 10-1, and the data transfer amount of the loop 10-1 has a limit value for the data read performance by the prefetch function. When data is read from the parity disks P1 to P4 by the prefetching function, the load on the loop 10-2 side is only offset and the problem is not solved.

An object of the present invention is to provide a disk subsystem having a mirrored disk device in which data is striped and having a configuration for improving the data read throughput performance by a prefetch function. Is to do.

Another object of the present invention is to provide a disk subsystem having a function of controlling to improve the throughput performance of data read by a prefetch function for a mirrored disk device.

[0007]

SUMMARY OF THE INVENTION The present invention has a disk controller and a plurality of mirrored disk devices. The mirrored disk device has a first device group in which data is striped and a first device group. And a second device group that is a mirror of the device group of
The disk subsystem is characterized in that individual devices constituting the disk device are connected to the disk control device via different transmission paths.

Further, the present invention is a disk subsystem configured so that at least a first device group and a second device group of a mirrored disk device are connected to a disk controller via different transmission paths. The disk controller performs control to determine a transmission path and a device group to be used so that a plurality of transmission paths are distributed and used for data transfer with respect to data reading by a prefetch function for a mirrored disk apparatus. It features a disk subsystem having means.

[0009]

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

FIG. 1 is a configuration diagram of the disk subsystem of the first embodiment. The disk subsystem includes a disk control device 8, a plurality of disk devices 12, and loops 10-1 and 10-2 for connecting the two. The disk control device 8 is connected to the host computer of the host device. The disk device 12 is a mirrored disk device, and includes a data disk Di and a parity disk Pi. The same data is stored in the parity disk Pi paired with the data disk Di. Loop 1
Reference numerals 0-1 and 10-2 denote transmission paths such as a fiber channel.
Loop control units 11-1 and 11-2 and the disk device 12
Are connected to the data disk Di (i = 1, 2, 3, 4) and the parity disk Pi. A bus such as SCSI may be used as the transmission path instead of the fiber channel. The loop control units 11-1 and 11-2 respectively control the loop 10-
It communicates with the data disk Di and the parity disk Pi via 1 and 10-2, and controls data transfer between the disk control device 8 and the disk device 12. Data disk Di
The parity disk Pi is an independent device (drive), and has a loop control unit and a device control unit, but is not shown. The disk control device 8
It has a cache memory, and temporarily stores data blocks transferred between the host device and the disk device 12 by the cache memory.

FIG. 2 is a diagram showing a data structure of a read device table stored in a storage device in the disk control device 8. This table is used when a data read command by the prefetch function is received from the host device. The target device is a device for which data is to be read, and sets an identifier of a loop to which the device is connected and an identifier of the device. The used device is a device that is actually used for data reading, and sets an identifier of a loop to which the device is connected and an identifier of the device. In this example, a setting is made such that when accessing an odd-numbered device, a data disk is accessed via a loop 10-1, and when accessing an even-numbered device, a parity disk is accessed via a loop 10-2. . That is, for the data read by the prefetch function, the transmission path and the device to be used are set so that the loads of the data transfer using the loop 10-1 and the data transfer using the loop 10-2 are distributed. Needless to say, the setting may be such that the data disk is accessed via the loop 10-1 when accessing the even numbered device, and the parity disk is accessed via the loop 10-2 when accessing the odd numbered device. .

FIG. 3 is a flowchart showing a processing flow of a part related to the present invention in the processing of the disk control device 8. When the disk control device 8 receives a command from the host device (step 21), if the command is a read command by the prefetch function (step 22YE).
S), referring to the read device table, determine a device to be used corresponding to the device to be accessed (step 23), and send a read command to the device to be used via the determined loop L1 or L2 (step 2).
4) Receive the data block from the device and store it in the cache memory. If the received command is not a read command by the prefetch function (step 22N)
O), perform the conventional command processing (step 2)
5).

The data disks D1 and D2, D3 and D
As shown in FIG. 4, data may be striped for a series of device groups. The lead device in that case
The table shows, for the target device groups L1 and D1-D2, the used device groups L1 and D1-D2;
D3-D4 is set as used device groups L2, P3-P4. In addition, in the processing procedure of the disk control device 8, the term "target device, used device" may be replaced with the target device group, used device group.

FIG. 4 is a configuration diagram of the disk subsystem of the second embodiment. The disk subsystem includes a disk control device 9, a plurality of disk devices 13, and loops 10-1, 10-2, 10-3, and 10-4 connecting the two.
Consists of The disk unit 13 is a mirrored disk unit, each of which is D1 and D2, D3 and D4 or D5.
, And data D6, and a parity disk Pi is provided for each data disk Di. Loops 10-1, 10-2, 10-
Reference numerals 3 and 10-4 denote transmission paths such as Fiber Channel and SCSI, and the loop control unit 11 of the disk control device 9.
-1 is the data disk D1, D via the loop 10-1.
3, D5, the loop controller 11-2 is connected to the parity disks P1, P3, P5 via the loop 10-2, and the loop controller 11-3 is connected to the data disks D2, D4, D6 via the loop 10-3. , The loop control unit 11-4 performs loop 1
It is connected to the parity disks P2, P4, and P6 via 0-4, and performs data transfer between the disk controller 9 and the device via the connected transmission line and loop control unit. As in the first embodiment, the data disk Di and the parity disk Pi are independent devices, respectively.
It has a loop control unit and a device control unit. In the present embodiment, the disk device 13 is a single mirrored disk device, but this is for the convenience of logical handling, and physically, one disk device 13 is physically mounted in several device housings. It may be divided.

FIG. 5 is a diagram showing a data structure of a device connection table stored in a storage device in the disk control device 9. This table shows the correspondence between the connected devices and the loops to which they are connected. Loop 10-1 to 1
0-4 constitute loop groups L1-L3 and L2-L4. For example, the device group D1-D2 that is data striped is connected to the loop group L1-L3, and the device group P1-P2 is connected to the loop group L2-L4, but both device groups have the same data content. Therefore, the disk control device 9 may read data of any device group.

FIG. 6 is a diagram showing a data structure of the loop load status table stored in the storage device in the disk control device 9. This table is a table used when a data read command by the prefetch function is received from the host device, and counts the number of read commands by the prefetch function during the processing of each of the loop groups L1-L3 and L2-L4. The number of in-process commands of each loop group is a numerical value representing the magnitude of the data transfer load applied to the loop group, and has an initial value of 0. Further, the number of other in-process commands may be counted for each loop group.

FIG. 7 is a flowchart showing a processing flow of a part related to the present invention in the processing of the disk control device 9. When the disk control device 9 receives a command from the host device (step 31), if the command is a read command by the prefetch function (step 32YE).
S), referring to the loop load status table (step 3)
3), loop group (L1-L3) and loop group (L2-L)
Compare the number of commands in process 4) (Step 3)
4). If the number of commands of (L1-L3)> the number of commands of (L2-L4) (step 35>), since the former has a larger loop load, the L2-L4 connection is referred to by referring to the device connection table. A device group is selected (step 36). That is, the target device group and the loop group (L
2-L4) is used as the used device group. (L1-L3) command number = (L
If the number of commands is (2-L4) (step 35 =),
The device group of the L1-L3 connection is selected with reference to the device connection table (step 37). That is, the target device group itself is a used device group. If the loop load status table counts the number of other commands in process, a device group connected to a loop group having a small number of other commands may be selected. If the number of commands of (L1-L3) <the number of commands of (L2-L4) (step 35 <), since the latter has a larger loop load, the L1-L3 connection is referred to by referring to the device connection table. A device group is selected (step 38). Next, 1 is added to the number of read commands by the prefetch function for the selected loop group in the loop load status table (step 3).
9) A read command is sent to the used device group via the selected loop group (step 40), and a data block is received from the device group and stored in the cache memory. When the read command processing by the prefetch function is completed, 1 is subtracted from the number of read commands by the prefetch function for the selected loop group.

If the received command is not a read command by the pre-reading function (NO at step 32), the command processing is performed as usual (step 41). However, if the number of other commands is counted for the loop group in the loop load status table, one is added to the number of commands for the loop group used at the start of the command processing, and the number of commands is set for the loop group used at the end of the command processing. Subtract 1 from the number.

The same applies to the case where data is striped over three or more disks. If each data device group and its parity device group are connected to another loop, the same device connection table and By referring to and updating the loop load status table, the data transfer load on the loop can be distributed by the data read having the prefetch function.

Further, it is easy to apply the method of the second embodiment to the disk subsystem having the structure of the first embodiment. In that case, the device group and the loop group in the device connection table and the loop load status table may be replaced with a single device and a single loop. Conversely, it is easy to apply the method of the first embodiment to a disk subsystem having the configuration of the second embodiment. In this case, the “connection loop” and “device” of the target device and the used device in the read device table may be replaced with “connection loop group” and “device group”.

Here, the data read performance that can be achieved by the difference in the configuration of the disk subsystem will be described.
The number of transmission lines such as loops 10-1, 10-2,... Is n, and the number of striping drives is m (there is a mirror disk, so the total number of mirrored disk devices is m × 2). If the upper limit of the amount of data transfer per transmission path is k by counting the number of drives capable of simultaneously transferring data, the maximum number of data read multiplicity that can be achieved by the prefetch function is (k / m) × n.

For example, if n = 2, m = 1 and k = 4 in the disk subsystem configuration of FIG. 1, the maximum multiplicity is 8
Becomes When n = 2, m = 2, and k = 4, the maximum multiplicity is 4. In the disk subsystem configuration of FIG. 4, since n = 4 and m = 2, the maximum multiplicity is 8 when k = 4. In the configuration of FIG. 8, since n = 2 and m = 4, the maximum multiplicity is 2 when k = 4,
This is the case where the present invention is applied. According to the prior art, since only the drive connected to the loop 10-1 is accessed, the maximum multiplicity is limited to one.

[0023]

As described above, according to the present invention, since the individual devices constituting the mirrored disk device are connected to the disk controller via different transmission paths, data striping can be performed. Even in a mirrored disk device that has been made, data read by a plurality of prefetch functions can be executed in parallel, and the throughput performance of data read by the prefetch function can be improved. Also, the disk controller
Since the load on the transmission path connecting the disk control device and the device group constituting the mirrored disk device is controlled to be distributed, the throughput performance of data read by the prefetch function can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a disk subsystem according to a first embodiment.

FIG. 2 is a diagram illustrating a data configuration of a read device table according to the first embodiment.

FIG. 3 is a flowchart illustrating a processing flow of a disk control device 8 according to the first embodiment.

FIG. 4 is a configuration diagram of a disk subsystem according to a second embodiment.

FIG. 5 is a diagram illustrating a data configuration of a device connection table according to the second embodiment.

FIG. 6 is a diagram illustrating a data configuration of a loop load status table according to the second embodiment.

FIG. 7 is a flowchart illustrating a processing flow of a disk control device 9 according to the second embodiment.

FIG. 8 is a diagram showing a configuration example of a conventional disk subsystem.

[Explanation of symbols]

8, 9: disk controller, 10: loop, 11: loop controller, 12, 13: disk device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuzo Kobashi 2880 Kozu, Odawara-shi, Kanagawa F-term in Storage Systems Division, Hitachi, Ltd. F-term (reference) 5B065 BA01 CA30 CC08 CH05 ZA13 5D066 BA02 BA08

Claims (5)

[Claims] 1. A system comprising: a disk controller; and a plurality of mirrored disk devices, wherein the mirrored disk device is a first device group in which data is striped and a mirror of the first device group. A disk subsystem, comprising: a plurality of device groups; and wherein individual devices constituting the mirrored disk device are connected to the disk control device via different transmission paths. 2. A system according to claim 1, further comprising a disk controller and a plurality of mirrored disk devices, wherein said mirrored disk device serves as a first device group in which data is striped and a mirror of the first device group. A disk subsystem, wherein at least a first device group and a second device group are connected to the disk controller via different transmission paths, respectively. The control device controls the transmission line and the device group to be used so that a plurality of the transmission lines are distributed and used for the data transfer with respect to the data read by the prefetch function to the mirrored disk device. A disk subsystem comprising: 3. The disk subsystem according to claim 2, wherein each of the first device group and the second device group is a single device instead of a set of striped devices. 4. A disk controller, comprising: a plurality of mirrored disk devices, wherein the mirrored disk device is a first device group on which data is striped and a mirror of the first device group. A disk subsystem, wherein at least a first device group and a second device group are connected to the disk controller via different transmission paths, respectively. The control device is configured to use a transmission line used for each mirrored disk device and a device to be used so that a plurality of the transmission lines are distributed and used for data transfer with respect to data read by the prefetch function for the mirrored disk device. A disk subsystem characterized by setting a group. 5. A disk controller, comprising: a plurality of mirrored disk devices, wherein the mirrored disk device is a first device group in which data is striped and a mirror of the first device group. A disk subsystem, wherein at least a first device group and a second device group are connected to the disk controller via different transmission paths, respectively. The control device, for the data read by the look-ahead function for the mirrored disk device, as a plurality of the transmission lines are used for data transfer in a distributed manner, a transmission line used in accordance with the data read in process and A disk subsystem for dynamically selecting a device group to be used.