Expansion of RAID subsystems using spare space with immediate access to new space

• US 20030115412A1
• Filed: 12/19/2001
• Published: 06/19/2003
• Est. Priority Date: 12/19/2001
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: RAIDCore, Inc. (Broadcom, Inc.)
• Inventors: Franklin, Chris R., Wong, Jeffrey T.
• Granted Patent: US 7,111,117 B2
• Time in Patent Office: Days
• US Class Current: 711/114
• CPC Class Codes: G06F 11/1092 Rebuilding, e.g. when physically replacing a failing disk
• CPC Class Codes: G06F 11/1096 Parity calculation or recalculation after configuration or reconfiguration of the system
• CPC Class Codes: G06F 2003/0697 device management, e.g. handlers, drivers, I/O schedulers
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems

Abstract

A method to expand a RAID subsystem from a first array of disk drives to a second array of disk drives. The first array includes a set of data disk drives storing old data and spare space, and the second array includes the first array and at least one new disk drive. First, the old data are distributed among the set of data disk drives and at least one new disk drive while, at the same time, new data are mapped to the spare space. Upon completion of the distribution, the new data are copied from the spare space to the set of data disk drives and at least one new disk drive to enable concurrent expansion of the first array while accessing the old and the new data.

Claims

1. A method for expanding a RAID subsystem from a first array of disk drives to a second array of disk drives, the first array including a set of data disk drives storing old data and spare space, and the second array including the first array and at least one new disk drive, comprising:

distributing the old data among the set of data disk drives and at least one new disk drive while mapping new data to the spare space; and

copying, upon completion of the distribution, the new data from the spare space to the set of data disk drives and at least one new disk drive to enable concurrent expansion of the first array while accessing the old and the new data.

2. The method of claim 1 further comprising:

allocating the spare space on a dedicated spare disk drive.

3. The method of claim 1 further comprising:

allocating the spare space among the first array of disk drives.

4. The method of claim 1 wherein the new data are mapped redundantly.

5. The method of claim 1 further comprising:

initializing the spare space to all zero data.

6. The method of claim 5 further comprising:

generating parity data for the initialized spare space.

7. The method of claim 1 further comprising:

initializing at least one new disk drive; and

generating parity data for the initialized new disk drive.

8. The method of claim 1 further comprising:

determining parity data for the new data from the new data and the old data.

9. An expandable RAID subsystem, comprising:

a first array of disk drives including a set of data disk drives storing old data and spare space;

a second array of disk drives including the first array and at least one new disk drive;

means for distributing the old data among the set of data disk drives and at least one new disk drive while mapping new data to the spare space; and

means for copying, upon completion of the distributing, the new data from the spare space to the set of data disk drives and at least one new disk drive to enable concurrent expansion of the first array while accessing the old and the new data.

10. The subsystem of claim 9 wherein the spare space is distributed and initialized to zero.

11. The subsystem of claim 9 where the spare space is allocated to an initialized dedicated disk drive.