Real time disk array which guarantees write deadlines by selecting an alternate disk

• US 6,021,464 A
• Filed: 09/10/1997
• Issued: 02/01/2000
• Est. Priority Date: 09/13/1996
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Torii, Osamu, Kanai, Tatsunori, Maeda, Seiji, Yao, Hiroshi, Kizu, Toshiki
• Primary Examiner(s): Cabeca, John W.
• Assistant Examiner(s): Chow, Christopher S.
• Application Number:
  US08/927,015
• Time in Patent Office: 874 Days
• Field of Search: 711/113, 711/114, 711/168, 348/7
• US Class Current: 711/114
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: H04N 21/21 Server components or server architectures
• CPC Class Codes: H04N 21/23 Processing of content or additional data; Elementary server operations; Server middleware

Abstract

The system and method store data into disk devices without loss of data, even when write requests having time limits are concentrated on a specific disk. When a write request for a given disk device is issued, if it is determined that some of this write request and other access requests having time limits for this disk device would not be executed within the respective time limits, the system writes the data temporarily into another disk device.

Claims

1. A data storage device, comprising:

a plurality of disk devices;

a module for storing a plurality of access requests for each of the plurality of disk devices;

a module for receiving a write request having a time limit;

a module for selecting one of the plurality of disk devices for the write request if it is determined that all of the access requests having time limits for the selected disk device and the write request can be executed within the respective time limits on the selected disk device; and

a module for scheduling the plurality of access requests for the selected disk device and the write request and instructing the selected disk device to execute the scheduled access requests and write request.

2. The device according to claim 1, wherein the module for selecting further includes

a submodule for selecting a disk device with a highest priority among the disk devices.

3. The device according to claim 2, wherein the module for selecting further includes

a submodule for determining that a disk device designated in the write request has the highest priority, when the write request includes information designating the disk device.

4. The device according to claim 1, further comprising

a module for reallocating data written on the selected disk device onto a disk device designated in the write request when the selected disk device is different from the designated disk device.

5. A data storage device, comprising:

a plurality of disk devices;

a module for storing a plurality of access requests for each of the plurality of disk devices;

a module for receiving a write request having a time limit and including information designating one of the plurality of disk devices; and

a module for selecting a different one of the plurality of disk devices from the designated disk device for the write request when it is determined that some of the access requests having time limits for the designated disk device and the write request cannot be executed within the respective time limits on the designated disk device.

6. The device according claim 5, further comprising

a module for scheduling the plurality of access requests for the selected disk device and the write request so that all of the access requests having time limits for the selected disk device and the write request are executed within the respective time limits, to instruct the selected disk device to execute the plurality of access requests and the write request.

7. The device according to claim 5, further comprising

a module for reading out data written on the selected disk device and writing the read data onto the designated disk device after the write request is executed.

8. The device according to claim 7, wherein the module for reading and writing includes

a module for determining a timing of the reading and a timing of the writing so as not to affect execution of all of the access requests having time limits within the respective time limits.

9. The device according to claim 5, wherein the module for selecting includes

a module for selecting a disk device as the different disk device by giving a higher priority to a disk device having a lighter load.

10. The device according to claim 5, wherein the module for selecting includes

a module for selecting a disk device as the different disk device by giving a higher priority to a disk device having more free memory capacity.

11. The device according to claim 5, wherein the module for selecting includes

a module for selecting the different disk device at random among the plurality of disk devices.

12. A method of controlling a data storage device having a plurality of disk devices, comprising steps of:

storing a plurality of access requests for each of the plurality of disk devices;

receiving a write request having a time limit;

selecting one of the plurality of disk devices for the write request so that all of the access requests having time limits for the selected disk device and the write request are executed within the respective time limits on the selected disk device; and

scheduling the plurality of access requests for the selected disk device and the write request to instruct the selected disk device to execute the scheduled access requests and write request.

13. The method according to claim 12, wherein the step of selecting includes a step of

determining whether or not all the access requests having time limits for a given one of the plurality of disk devices and the write request can be executed within the respective time limits on the given disk device.

14. The method according to claim 12, wherein the step of selecting further includes a step of

selecting a disk device with a highest priority among the disk devices determined affirmatively at the step of determining.

15. The method according to claim 14, wherein the step of selecting further includes a step of

determining that a disk device designated in the write request has the highest priority, when the write request includes information for designating the disk device.

16. The method according to claim 12, further comprising a step of

reallocating data written on the selected disk device onto a disk device designated in the write request, when the selected disk device is different from the designated disk device.

17. A method of controlling data storage device having a plurality of disk devices, comprising steps of:

storing a plurality of access requests for each of the plurality of disk devices;

receiving a write request having a time limit and including information for designating one of the plurality of disk devices;

selecting a different one of the plurality of disk devices from the designated disk device for the write request, when it is determined that some of the access requests having time limits for the designated disk device and the write request cannot be executed within the respective time limits on the designated disk device; and

scheduling the plurality of access requests for the selected disk device and the write request so that all of the access requests having time limits for the selected disk device and the write request are executed within the respective time limits, to instruct the selected disk device to execute the plurality of access requests and the write request.

18. The method according claim 17, further comprising a step of

storing a correspondence between the selected disk device and the designated disk device.

19. The method according to claim 17, further comprising a step of

reading out data written on the selected disk device and writing the read data onto the designated disk device, after the write request is executed.

20. The method according to claim 19, wherein the step of reading and writing includes a step of

determining a timing of the reading and a timing of the writing so as not to affect execution of all of the access requests having time limits within the respective time limits.

21. The method according to claim 17, wherein the step of selecting includes a step of

selecting a disk device as the different disk device, by giving a higher priority to a disk device having a lower load.

22. The method according to claim 17, wherein the step of selecting includes a step of

selecting a disk device as the different disk device, by giving a higher priority to a disk device having more free memory capacity.

23. The method according to claim 17, wherein the step of selecting includes a step of

selecting the different disk device at random among the plurality of disk devices.