Method for performing a RAID stripe write operation using a drive XOR command set

• US 5,742,752 A
• Filed: 12/29/1995
• Issued: 04/21/1998
• Est. Priority Date: 12/29/1995
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Symbios Logic Incorporated (Broadcom, Inc.)
• Inventors: DeKoning, Rodney A.
• Primary Examiner(s): Decady, Albert
• Application Number:
  US08/581,153
• Time in Patent Office: 844 Days
• Field of Search: 395/182.03, 395/182.04, 395/182.05, 395/182.06, 395/427, 395/441, 395/438, 395/439, 371/51.1
• US Class Current: 714/6.22
• 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

Method for implementing a stripe write operation in a RAID device having XOR command set enabled disk drives on a common interface bus. The method of the present invention improves upon prior designs which do not use the XOR command set by eliminating the need for the RAID controller to include XOR (parity) generation computational elements. Further, the method of the present invention improves upon the stripe write method suggested by the XOR command set specifications in which a stripe is performed by a series of xdwrite XOR command operations issued to the data drives of the RAID array. Rather, the method of the present invention performs parallel standard writes of the data portions of the stripe write, then issues a rebuild XOR command to the parity disk drive to rapidly regenerate the parity blocks in the stripe just written. The method of the present invention reduces the worst case rotational latency delay of the stripe write operation to two rotational latency periods.

Claims

1. In a RAID controller for controlling a RAID storage subsystem having at least one disk array comprising a plurality of XOR command set enabled disk drives, a method operable within said RAID controller for performing a stripe write of data to said disk array, said method comprising the steps of:

initiating write operations to all disk drives which contain data in the stripe to be written; and

initiating, responsive to completion of said write operations, an XOR command set rebuild command to the disk drive containing parity information in the stripe.

2. The method of claim 1 wherein said write operations are performed in parallel.

3. In a RAID subsystem having a disk array comprising a plurality of data disk drives and at least one XOR command set enabled parity disk drive, a method operable within a RAID controller for performing a write of data to said disk array, said method comprising the steps of:

initiating write operations to a subset of said data disk drives; and

initiating an XOR command set rebuild command to said at least one XOR command set enabled parity disk drive.

4. The method of claim 3 wherein said write operations are performed in parallel.

5. The method of claim 3 wherein the step of initiating a rebuild is responsive to completion of the write operations.

6. The method of claim 3 wherein said subset is all of said plurality of data disk drives.

7. A RAID controller for controlling a RAID subsystem having a disk array comprising a plurality of data disk drives and at least one XOR command set enabled parity disk drive, said RAID controller comprising:

means for initiating write operations to a subset of said data disk drives; and

means, responsive to said means for initiating write operations, for initiating an XOR command set rebuild command to said at least one XOR command set enabled parity disk drive.

8. The RAID controller of claim 7 wherein said write operations are performed in parallel.

9. The RAID controller of claim 7 wherein said subset is all of said plurality of data disk drives.