Apparatus and method for performing a preemptive reconstruct of a fault-tolerant RAID array

• US 7,313,721 B2
• Filed: 08/04/2004
• Issued: 12/25/2007
• Est. Priority Date: 06/21/2004
• Status: Active Grant

• Current Assignee: Dot Hill Systems Corporation (Seagate Technology Holdings Plc)
• Original Assignee: Dot Hill Systems Corporation (Seagate Technology Holdings Plc)
• Inventors: Ashmore, Paul Andrew
• Primary Examiner(s): Maskulinski; Michael C
• Application Number:
  US10/911,110
• Publication Number:
  US 20050283655A1
• Time in Patent Office: 1,238 Days
• Field of Search: 714/7
• US Class Current: 714/6.32
• CPC Class Codes: G06F 11/004 Error avoidance G06F11/07 and subgroups take precedence
• CPC Class Codes: G06F 11/008 Reliability or availability analysis
• CPC Class Codes: G06F 11/1084 Degraded mode, e.g. caused by single or multiple storage removals or disk failures
• CPC Class Codes: G06F 11/1092 Rebuilding, e.g. when physically replacing a failing disk
• CPC Class Codes: G06F 11/1662 the resynchronized component or unit being a persistent storage device re-synchronization of failed mirror storage G06F11/2082; rebuild or reconstruction of parity RAID storage G06F11/1008
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence
• CPC Class Codes: G06F 2211/1035 Keeping track, i.e. keeping track of data and parity changes

Abstract

A RAID controller performs a preemptive reconstruct of a redundant array of disks while it is still fault-tolerant by determining the errors by a first disk exceeded the error threshold, and reading data from a second disk, and writing the data to a spare disk. The second disk'"'"'s data is a mirrored copy of the first disk'"'"'s data. The controller also replaces the first disk with the spare disk, after completing the reading and writing. Additionally, while performing the reading and writing, the controller writes second data to the first disk in response to a user write request including the second data, thereby maintaining the fault-tolerance of the redundant array. In another embodiment, the controller creates the data of the first disk from second data read from two or more of the other disks in the array and writes the created data to the spare disk.

Claims

1. A method for performing a preemptive reconstruct of a redundant array of disks while the redundant array is still fault-tolerant, the method comprising:

determining that a number of errors by one of the disks in the redundant array has exceeded an error threshold;

reading data from a second one of the disks in the redundant array and writing the data to a spare disk, in response to said determining, wherein the data of the second one of the disks in the redundant array is a mirrored copy of data of the one of the disks;

replacing the one of the disks in the redundant array with the spare disk, after said reading and writing is complete; and

while said reading and writing, writing second data to the one of the disks in the redundant array in response to a user write request including the second data, thereby maintaining the fault-tolerance of the redundant array.

2. The method of claim 1, further comprising:

writing the second data also to the spare disk if a destination of the second data is to a location previously written to the spare disk by said reading and writing.

3. A method for performing a preemptive reconstruct of a redundant array of disks while the redundant array is still fault-tolerant, the method comprising:

determining that a number of errors by one of the disks in the redundant array has exceeded an error threshold;

creating the data of the one of the disks from second data read from two or more of the other disks in the redundant array and writing the created data to a spare disk, in response to said determining;

replacing the one of the disks in the redundant array with the spare disk, after said creating and writing is complete; and

while said creating and writing, writing third data to the one of the disks in the redundant array in response to a user write request including the third data, thereby maintaining the fault-tolerance of the redundant array.

4. The method of claim 3, wherein said creating the data comprises:

reading the second data from the two or more of the other disks in the redundant array; and

performing a binary exclusive-OR of the second data to generate the data of the one of the disks.

5. The method of claim 3, further comprising:

writing the third data also to the spare disk if a destination of the third data is to a location previously written to the spare disk by said creating and writing.

6. A RAID controller for performing a preemptive reconstruct of a redundant array of disks while the redundant array is still fault-tolerant, comprising:

a memory, for storing an error threshold; and

a microprocessor, coupled to said memory, configured to;

determine that a number of errors by one of the disks in the redundant array has exceeded the error threshold;

read data from a second one of the disks in the redundant array and write the data to a spare disk, in response to determining that the number of errors exceeded the error threshold, wherein the data of the second one of the disks in the redundant array is a mirrored copy of data of the one of the disks;

replace the one of the disks in the redundant array with the spare disk, after the reading of the data and the writing of the data to the spare disk is complete; and

while performing the reading and writing, write second data to the one of the disks in the redundant array in response to a user write request including the second data, thereby maintaining the fault-tolerance of the redundant array.

7. The RAID controller of claim 6, wherein the microprocessor is further configured to:

write the second data also to the spare disk if a destination of the second data is to a location previously written to the spare disk by the reading and writing.

8. A RAID controller for performing a preemptive reconstruct of a redundant array of disks while the redundant array is still fault-tolerant, comprising:

a memory, for storing an error threshold; and

a microprocessor, coupled to said memory, configured to;

determine that a number of errors by one of the disks in the redundant array has exceeded the error threshold;

create the data of the one of the disks from second data read from two or more of the other disks in the redundant array and write the created data to a spare disk, in response to determining that the number of errors exceeded the error threshold;

replace the one of the disks in the redundant array with the spare disk, after the creating of the data and the writing of the created data to the spare disk is complete; and

while performing the creating and writing, write third data to the one of the disks in the redundant array in response to a user write request including the third data, thereby maintaining the fault-tolerance of the redundant array.

9. The RAID controller of claim 8, wherein in order to create the data, the microprocessor is configured to:

read the second data from the two or more of the other disks in the redundant array; and

perform a binary exclusive-OR of the second data to generate the data of the one of the disks.

10. The RAID controller of claim 8, the microprocessor is configured to:

write the third data also to the spare disk if a destination of the third data is to a location previously written to the spare disk by the creating and writing.