Data storage device and data managing method

• US 5,485,475 A
• Filed: 08/31/1994
• Issued: 01/16/1996
• Est. Priority Date: 09/22/1993
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Takagi, Shiro
• Primary Examiner(s): Envall, Jr., Roy N.
• Assistant Examiner(s): BROWN, THOMAS
• Application Number:
  US08/298,275
• Time in Patent Office: 503 Days
• Field of Search: 371/10.1, 371/10.2, 371/10.3, 371/11.1, 371/21.1, 371/21.2, 371/40.1-40.4, 371/51.1, 371/68.1, 364/268.5, 364/268.2
• US Class Current: 714/766
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: Y10S 707/99931 Database or file accessing

Abstract

A data storage device includes a plurality of data disks for storing data in units of data blocks and a parity disk for storing parity data used for restoring data to the data disks. Data blocks on the respective data disks are managed with respect to whether each data block is used for data storage and managed with respect to whether data of each data block is used for computing parity. Each data block which is not used for data storage and is used for computing parity is detected. The parity data are updated based on data in the detected data blocks and the parity data stored to the parity disk corresponding to the detected data blocks.

Claims

1. A data storage device comprising:

a plurality of data disks for storing data in units of data blocks;

a parity disk for storing parity data used for restoring data to the data disks;

first managing means for managing data blocks on the respective data disks with respect to whether each data block is used for data storage;

second managing means for managing the data blocks on the respective data disks with respect to whether data of each data block is used for computing parity;

detecting means, responsive to the first and second managing means, for detecting each data block which is not used for data storage and is used for computing parity; and

purge processing means for updating the parity data based on data in the data blocks detected by the detecting means and the parity data stored to the parity disk corresponding to the detected data blocks.

2. A device according to claim 1, wherein the first managing means includes first flag storage means for storing first flag information representing whether each data block on the respective data disks is used for data storage.

3. A device according to claim 1, wherein the second managing means includes second flag storage means for storing second flag information representing whether data of each data block is used for computing parity.

4. A device according to claim 1 further comprising means for further updating the parity data stored to the parity disk based on the parity data and data newly written to a selected data block when, prior to newly writing, the selected data block is not used for data storage and not used for computing parity.

5. A data storage device comprising:

a plurality of first storage media for storing file data in units of data blocks;

a second storage medium for storing in parity blocks parity data corresponding to data stored in corresponding blocks in the respective first storage media;

first flag storage means for storing first flag data showing whether each data block is used as a file data area;

second flag storage means for storing second flag data showing whether each data block is used for computing parity;

detecting means, responsive to the first and second flag storage means, for detecting each data block not used as a file data area and used for computing parity;

purge processing means for updating the contents of the parity blocks based on data in the data blocks detected by the detecting means and the parity data in the parity blocks corresponding to the detected data block, and for toggling the second flag data for the detected data block; and

parity data generating means for judging whether a selected one of the data blocks is not used for computing parity based on the second flag data when data is newly written in the selected data block, for updating the contents of the parity block corresponding to the selected data block based on parity data of the parity block corresponding to the selected data block and data to be newly written to the selected data block, and for toggling the second flag data for the selected data block.

6. A device according to claim 5, further comprising:

access detecting means for detecting presence of a request for accessing files; and

means for starting the purge processing means when the access detecting means detects an absence of a file accessing request.

7. A data storage device comprising:

a plurality of first storage media for storing file data in units of data blocks;

a second storage medium for storing in parity blocks parity data corresponding to data stored in corresponding blocks in the respective first storage media;

first flag storage means for storing first flag data showing whether each data block is used as a file data area;

second flag storage means for storing second flag data showing whether each data block is used for computing parity;

detecting means, responsive to the first and second flag storage means, for detecting each data block not used as a file data area and used for computing parity;

purge processing means for updating the contents of the parity blocks based on data in the data blocks detected by the detecting means and the parity data in the parity blocks corresponding to the detected data block, and for toggling the second flag data for the detected data block; and

data restoration means for restoring data in a selected one of the data blocks of a selected one of the first storage media based on parity data in the parity block corresponding to the selected data block and data in the corresponding data block on a non-selected one of the first storage media which is used for computing parity.

8. A device according to claim 7, further comprising:

access detecting means for detecting presence of a request for accessing files; and

means for starting the purge processing means when the access detecting means detects an absence of a file accessing request.

9. A device according to claim 7, wherein the data restoration means includes XOR operating means for executing an exclusive OR (XOR) operation between parity data in the parity block corresponding to the selected data block and data in the corresponding data block on the non-selected one of the first storage media.

10. A data managing method for a data storage device including a plurality of first storage media for storing file data in units of data blocks and second storage medium for storing in parity blocks parity data corresponding to data stored in corresponding blocks in the respective first storage media, comprising the steps of:

storing first flag data showing whether each data block is used as a file data area;

storing second flag data showing whether each data block is used for computing parity;

detecting each data block not used as a file data area and used for computing parity;

updating the contents of the parity blocks based on data in the detected data blocks and the parity data in the parity blocks corresponding to the detected data block, and toggling the second flag data for the detected data block;

judging whether a selected one of the data blocks is not used for computing parity based on the second flag data when data is newly written in the selected data block;

updating the contents of the parity block corresponding to the selected data block based on parity data of the parity block corresponding to the selected data block and data to be newly written to the selected data block; and

toggling the second flag data for the selected data block.

11. A method according to claim 10, further comprising:

detecting presence of a request for accessing files; and

starting the purging step when the access detecting step detects an absence of a file accessing request.

12. A data managing method of a data storage device, including a plurality of first storage media for storing file data in units of data blocks and second storage medium for storing in parity blocks parity data corresponding to data stored in corresponding blocks in the respective first storage media, comprising the steps of:

storing first flag data showing whether each data block is used as a file data area;

storing second flag data showing whether each data block is used for computing parity;

detecting each data block not used as a file data area and used for computing parity;

updating the contents of the parity blocks based on data in the detected data blocks and the parity data in the parity blocks corresponding to the detected data block, and toggling the second flag data for the detected data block;

restoring data in a selected one of the data blocks of a selected one of the first storage media based on parity data in the parity block corresponding to the selected data block and data in the corresponding data block on a non-selected one of the first storage media which is used for computing parity.

13. A method according to claim 12, further comprising:

detecting presence of a request for accessing files; and

starting the purging step when the access detecting step detects an absence of a file accessing request.

14. A method according to claim 12, wherein the restoring step includes executing an exclusive OR (XOR) operation between parity data in the parity block corresponding to the selected data block and data in the corresponding data block on the non-selected one of the first storage media.