Methods, apparatus and controllers for a raid storage system

• US 7,506,187 B2
• Filed: 08/30/2004
• Issued: 03/17/2009
• Est. Priority Date: 09/02/2003
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Maddock, Robert Frank
• Primary Examiner(s): Lee; Thomas
• Assistant Examiner(s): Abbaszadeh; Jaweed A
• Application Number:
  US10/930,356
• Publication Number:
  US 20050050381A1
• Time in Patent Office: 1,660 Days
• Field of Search: 713/310, 711/114, 714/6, 714/7
• US Class Current: 713/310
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 11/2087 with a common controller
• CPC Class Codes: G06F 2211/1045 Nested RAID, i.e. implementing a RAID scheme in another RAID scheme

Abstract

Provided are RAID storage systems, methods, and controllers for RAID storage systems. A first method includes storing a first copy of the data in a first RAID array corresponding to a first RAID level providing redundancy (such as RAID-5), and storing a second copy of the data in a second RAID array corresponding to a second RAID level (such as RAID-0) which differs from the first RAID level. Data is read from the two RAID arrays in parallel for improved read performance. A controller is responsive to a disk failure which results in data becoming inaccessible from one of the arrays to retrieve the data from the other one of the arrays. The redundancy within the first RAID array also enables the controller to restore data following a failure of one disk drive by reference to the remaining disk drives of the first array.

Claims

1. A method of operating a RAID storage system, comprising:

storing a first copy of data in a first array of disk drives in accordance with a first RAID level providing redundancy;

storing a second copy of the data in a second array of disk drives in accordance with a second RAID level which differs from the first RAID level;

reading stored data by disk access operations performed on the first and second arrays; and

in response to a disk failure resulting in data becoming inaccessible from a first one of said arrays, reading the data from the other one of said arrays and restoring the data to the one of said arrays affected by the disk failure by copying the data from the other one of said arrays.

2. A method according to claim 1, further comprising:

sharing a read operation workload between the first and second arrays by performing a set of disk access operations in parallel on the first and second arrays.

3. A method according to claim 1, wherein storing the second copy of the data comprises performing non-redundant striping of data across the disk drives of the second array.

4. A method according to claim 1, wherein storing the first copy of the data comprises performing block-level striping of data across disk drives of the first array and storing parity information on one or more disk drives of the first array.

5. A method according to claim 4, including distributing parity information across disk drives of the first array.

6. A method to operate a RAID storage system, comprising:

storing a first copy of data in a first array of disk drives in accordance with a first RAID level providing redundancy;

storing a second copy of the data in a second array of disk drives in accordance with a second RAID level which differs from the first RAID level; and

in response to data becoming inaccessible for reading from a first one of said arrays, reading the data from the other one of said arrays and restoring the data to the affected one of said arrays by copying the data from the other one of said arrays.

7. A method according to claim 6, further comprising:

sharing a read operation workload between the first and second arrays comprising performing a set of disk access operations in parallel on the first and second arrays.

8. A method according to claim 6, wherein storing the second copy of the data comprises performing non-redundant striping of data across disk drives that comprise the second array.

9. A method according to claim 6, wherein storing the first copy of the data comprises performing block-level striping of data across disk drives that comprise the first array;

and storing parity information on at least one disk drive that comprises at least part of the first array.

10. A method according to claim 6, wherein storing the first copy of the data comprises performing block-level striping of data across disk drives that comprise the first array;

and distributing parity information across disk drives that comprise the first array.