Storage system, controller, control method and program product therefor

• US 20040250019A1
• Filed: 04/22/2004
• Published: 12/09/2004
• Est. Priority Date: 05/09/2003
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Sumiyoshi, Tohru, Terashita, Yoshihiko, Fujie, Yoshihiro
• Granted Patent: US 7,133,967 B2
• Time in Patent Office: Days
• US Class Current: 711/114
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 2211/1054 Parity-fast hardware, i.e. dedicated fast hardware for RAID systems with parity

Abstract

A storage system in which a set of a data block and a redundancy block is stored has a plurality of control sections which respectively control a plurality of storages, a host connection unit which selects the control section controlling one of the storage in which a write data block which is a write-object block is to be stored, and a transfer unit which transfers the write data block to the control section. Each of the plurality of control sections includes a data block write section which writes the write data block transferred by a transfer unit to the storage in which the write data block is to be stored, a redundancy block update request section which requests the control section controlling the storage in which a redundancy block is to be stored to update the redundancy block, and a redundancy block update section which updates the redundancy block stored in the storage controlled by the control section when another of the control sections makes a request for updating the redundancy block.

Claims

1. A storage system comprising:

a plurality of storages;

a plurality of control sections which respectively control the plurality of storages;

a host connection unit which receives from an external host system a write data block which is a data block to be stored in the plurality of storages, and which selects a control section controlling the storage in which the write data block is to be stored; and

a transfer unit which transfers the received write data block to said control section controlling the storage in which the write data block is to be stored.

2. The storage system of claim 1 wherein each of said plurality of control sections includes:

a data block write section which writes the write data block transferred from the transfer unit to the storage in which the write data block is to be stored;

a redundancy block update request section which requests said control section controlling the storage in which a redundancy block in the set including the write data block is to be stored to update the redundancy block; and

a redundancy block update section which updates the redundancy block stored in the storage controlled by said control section when another of said control sections makes a request for updating the redundancy block.

3. The storage system according to claim 1, wherein each of said plurality of control sections includes a data block readout section which reads out a data block stored in the storage area in the storage to which the write data block transferred by the transfer unit is to be written, before writing the write data block to the storage in which the write data block is to be stored;

an update data generation section which generates update data used for updating the redundancy block on the basis of the write data block transferred by said transfer unit and the stored data block;

a redundancy block readout section which reads out the redundancy block before updating data stored in the storage controlled by said control section when said another control section makes a request for updating the redundancy block; and

a redundancy block generation section which generates in the set including the write data block a new redundancy block corresponding to said redundancy block on the basis of the redundancy block before updating and the update data generated by said update data generation section,

wherein said redundancy block update section writes the redundancy block generated by said redundancy block generation section to the storage in which the redundancy block is to be stored.

4. The storage system according to claim 3, wherein said update data generation section generates the update data by performing exclusive OR operation on the write data block and the stored data block on a bit-by-bit basis, and

wherein said redundancy block generation section generates in the set including the write data block a new redundancy block corresponding to said redundancy block by performing exclusive OR operation on the redundancy block before updating and the update data on a bit-by-bit basis.

5. The storage system according to claim 2, wherein said data block write section writes the write data block transferred by said transfer unit to the storage controlled by said control section including said data block write section and to a mirror storage functioning as a mirror of said storage;

and

wherein when said redundancy block update section is requested by said another control section to update the redundancy block, it updates the redundancy blocks respectively stored in the storage controlled by said control section including said redundancy block update section and the mirror storage functioning as a mirror of said storage.

6. The storage system according to claim 5, wherein a first control section corresponding to said control section, the storage controlled by said first control section and a second mirror storage corresponding to said mirror storage and functioning as a mirror of the storage controlled by a second control section corresponding to said control section are mounted on a first sub assembly detachably mounted on an enclosure for the storage system, and

wherein said second control section, the storage controlled by said second control section and a first mirror storage corresponding to said mirror storage and functioning as a mirror of the storage controlled by said first control section are mounted on a second sub assembly detachably mounted on the enclosure for the storage system.

7. The storage system according to claim 6, further comprising:

a first selector which selects between electrical connection of said first control section to said first mirror storage and electrical connection of said first control section to said second mirror storage; and

a second selector which selects between electrical connection of said second control section to said second mirror storage and electrical connection of said second control section to said first mirror storage.

8. The storage system according to claim 7, wherein said first selector selects between electrical connection of said first control section to said second mirror storage and electrical connection of said first control section to said first mirror storage via said first selector and said second selector;

and

said second selector selects between electrical connection of said second control section to said first mirror storage and electrical connection of said second control section to said second mirror storage via said second selector and said first selector.

9. The storage system according to claim 7, wherein said second selector electrically connects said second control section to said first mirror storage when said first storage and/or said first control section fails;

and

wherein when a request for reading out the data block stored in said first storage is received from the host system in a state where said first storage and/or said first control section is faulty, said host connection unit reads out a data block which is a mirror of said data block from said first mirror storage by means of said second control section, and responds the read data block to the host system.

10. The storage system according to claim 1, wherein a set of a plurality of data blocks and a redundancy block which is redundancy data for regenerating at least one of the data blocks when the at least one of the data blocks becomes faulty is stored by being distributed to the plurality of storages,

wherein when a readout request for reading out an unreadable one of the data blocks is received from the external host system, said host connection unit transfers through said transfer unit the readout request to said control section controlling the storage in which the redundancy block in the set including the unreadable data block is stored.

11. The storage system according to claim 10 wherein each of said plurality of control sections further includes:

a redundancy block readout section which, in the case of receiving the request for reading out the unreadable data block, reads out the redundancy block in the set including the unreadable data block from the storage in which the redundancy block is stored;

a block readout request section which, in the case of receiving the request for reading out the unreadable data block, requests said another control section controlling the storage in which the normal data block in the set including the unreadable data block and the redundancy block is stored to read out the normal data block;

a data block regeneration section which regenerates the unreadable data block to the original state on the basis of the normal data block read out by said another control section according to the request from said block readout request section and the redundancy block; and

a data block respond section which responds the regenerated data block to the host system through said host connection unit.

12. The storage system according to claim 1, wherein said host connection unit includes:

a cache memory section which stores a data block read out in response to a readout request from the host system; and

a cache control section which responds the data block from said cache memory section to the host system when a readout request for reading out the data block stored in said cache memory section is received from the host system,

wherein said cache control section sets a higher priority with which a data block regenerated from a faulty state to the original state by a data block regeneration section remains in said cache memory section in comparison with the data block which has not been unreadable.

13. The storage system according to claim 1, wherein a set of a plurality of data blocks and a redundancy block which is redundancy data for regenerating at least one of the data blocks when the at least one of the data blocks becomes faulty is stored by being distributed to the plurality of storages,

wherein when a reconstruction request for regenerating an unreadable one of the data blocks to the original state and writing the regenerated data block to the storage in which the data block is to be stored is received from the external host system, said host connection unit transfers the request for reconstruction of the unreadable data block to said control section controlling the storage in which the data block is to be stored;

wherein each of said plurality of control sections further includes;

a block readout request section which requests some of the other control sections controlling the storage in which the data block or the redundancy block in the set including the unreadable data block is stored to read out the data block or the redundancy block in the set including the unreadable data block; and

a data block regeneration section which regenerates the unreadable data block on the basis of the data block and the redundancy block responded from some of the other control sections according to the request from said block readout request section, and

wherein said data block write section writes the data block regenerated by said data block regeneration section to the storage in which the data block is to be stored.

14. The storage system according to claim 2, wherein when said redundancy block update section updates the redundancy block, it transmits a redundancy block update notice to said control section that has requested update of the redundancy block, and

wherein said control section that has requested update of the redundancy block further includes a completion notice section which transmits a write completion notice to the host system through said host connection unit when the redundancy block update notice is received and when the write data block in the set including the redundancy block is written to the storage in which the write data block is to be stored.

15. A storage system comprising:

a plurality of storages;

a first control section which controls a first storage of the plurality of storages in which a first data block is stored and a second storage of the plurality of storages in which a first mirror block which is a mirror of the first data block is stored;

a second control section which controls a third storage of the plurality of storages in which a second data block is stored and a fourth storage of the plurality of storages in which a second mirror block which is a mirror of the second data block is stored;

a host connection unit which reads out the first data block from the first storage through said first control section and responds the first data block to an external host system when receiving from the host system a request for reading out the first data block, and which reads out the second data block from the third storage through said second control section and responds the second data block to the host system when receiving from the host system a request for reading out the second data block; and

a selector which establishes an electrical connection between said first control section and the fourth storage in place of an electrical connection between said first control section and the second storage when said second control section or the first storage fails.

16. The storage system of claim 15 further including a readout request signal from the host to read out data from the second data where said second control section is faulty, said host connection unit transfers the second data block readout request to said first control section, and the first control section receiving the second data block readout request reads out the second mirror block from the fourth storage electrically connected by said selector, and responds the second mirror block to said host connection unit.

17. A controller for a storage system in which a data block and a redundancy block which is redundancy data for regenerating the data block is to be stored comprising:

a data block write section which writes the write data block to the storage in which the write data block is to be stored;

a redundancy block update request section which requests a controller controlling the storage in which the redundancy block in the set including the write data block is to be stored to update the redundancy block; and

a redundancy block update section which updates the redundancy block stored in the storage controlled by said controller when another controller makes a request for updating the redundancy block.

18. A system comprising:

a selector which establishes an electrical connection between a controller and a second storage, storing mirror blocks which are mirrors of data blocks stored in a first storage, in place of an electrical connection between said controller and the first storage when a first controller or the first storage fails; and

a control section which reads out the mirror blocks from the second storage electrically connected by said selector and responds the second mirror block to a host connection unit when the second data block readout request is received in a state where said second controller is faulty.

19. A method comprising:

providing a plurality of storages;

providing a plurality of controllers wherein each controller controls at least one storage;

using a block write function for writing data block transferred from a transfer unit to the storage in which the write data block is to be stored;

using a redundancy block update request function for requesting a controller controlling the storage in which redundancy block in the set including the write data block is to be stored to update the redundancy block; and

using a redundancy block update function for updating the redundancy block stored in the storage controlled by said controller when another of said controllers makes a request for updating the redundancy block.

20. A system comprising:

a transfer function for causing a host connection unit to transfer a second data block readout request signal to a first controller when receiving the second data block readout request from a host system in a state where a second controller or a third storage is faulty;

a selector function for establishing an electrical connection between the first controller and a fourth storage in place of an electrical connection between said first controller and the second storage when said second controller or the third storage fails; and

a control function for causing said first controller to read out a second mirror block from the fourth storage electrically connected in said selector function and responding the second mirror block to said host connection unit when the second data block readout request is received in a state where said second controller is faulty.

21. A program product comprising:

a recording medium on which a computer program is recorded, said computer program including;

(a) a first instruction set which writes write data block transferred from a transfer unit to a storage in which the write data block is to be stored;

(b) a second instruction set which requests a control section controlling the storage in which a redundancy block in the set including the write data block is to be stored to update the redundancy block; and

(c) a third instruction set which updates the redundancy block stored in the storage controlled by said control section when another of said control sections makes a request for updating the redundancy block.