Redundant array of disk drives with asymmetric mirroring and asymmetric mirroring data processing method

• US 6,397,348 B1
• Filed: 07/23/1996
• Issued: 05/28/2002
• Est. Priority Date: 10/12/1994
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Styczinski, David A.
• Primary Examiner(s): Baderman, Scott T.
• Application Number:
  US08/685,269
• Time in Patent Office: 2,135 Days
• Field of Search: 395/182.04,182.05 371/40.1 714/6,7 707/202 711/114
• US Class Current: 714/6.12
• CPC Class Codes: G06F 11/2061 combined with de-clustering of data
• CPC Class Codes: G06F 11/2087 with a common controller
• CPC Class Codes: G11C 29/74 using duplex memories, i.e. using dual copies

Abstract

Apparatus and a method are provided for processing data in data processing system including a redundant array of independent disk drives (RAID) operatively controlled by an array controller. A plurality of data drives and a predefined mirror drive are provided by the RAID. The predefined mirror drive has a set capacity substantially greater than a capacity of each of the plurality of data drives. Data is written to and read from the multiple data drives in the RAID. A mirror copy of the data is written on a predefined mirror drive in the RAID.

Claims

1. A method for processing data in data processing system including a redundant array of independent disk drives (RAID) operatively controlled by an array controller comprising the steps of:

providing a plurality of data drives and a single predefined mirror drive in the RAID;

said single predefined mirror drive having a set capacity substantially greater than a capacity of each of said plurality of data drives;

writing data to multiple data drives in the RAID;

writing a mirror copy of said written data to said predefined mirror drive in the RAID; and

reading data from said multiple data drives.

2. A method for processing data in data processing system including a redundant array of independent disk drives (RAID) as recited in claim 1 further includes the step of:

temporarily storing write command data to a write cache; and

wherein said steps of writing data to multiple data drives and writing a mirror copy to said single predefined mirror drive in the RAID include the step of destaging data from said write cache.

3. A method for processing data in data processing system including a redundant array of independent disk drives (RAID) as recited in claim 1 wherein said step of reading data from said multiple data drives includes the steps of:

identifying a busy or failed data drive; and

reading data from said single predefined mirror drive in the RAID.

4. A method for processing data in data processing system including a redundant array of independent disk drives (RAID) as recited in claim 1 further includes the step of:

calculating data drives for writing data and identifying a failed data drive;

writing data for said failed data drive to said single predefined mirror drive in the RAID.

5. A method for processing data in data processing system including a redundant array of independent disk drives (RAID) as recited in claim 2 wherein said step of writing data to multiple data drives in the RAID includes the step of:

searching the write cache for destage data at higher addresses nearest a drive arm of said single predefined mirror drive;

writing said destage data to said multiple data drives; and

allocating the destage data space in write cache as available.

6. A data processing system including a redundant array of independent disk drives (RAID) operatively controlled by an array controller, said array controller comprising:

means for assigning a plurality of data drives and a single predefined mirror drive in the RAID;

said single predefined mirror drive having a set capacity substantially greater than a capacity of each of said plurality of data drives;

means for writing data to said plurality data drives in the RAID;

means for writing a mirror copy of said written data to said single predefined mirror drive in the RAID; and

means for reading data from said multiple data drives.

7. A data processing system as recited in claim 6 includes a write cache for temporarily storing write command data.

8. A data processing system as recited in claim 6 includes means for identifying a failed data drive and means for writing data for said identified failed data drive to said predefined mirror drive.

9. A data processing system as recited in claim 6 wherein said single predefined mirror drive has a predefined capacity greater than or equal to a sum of the capacity of said plurality of data drives.

10. A data processing system as recited in claim 6 includes means for identifying a failed data drive and means for reading data from said single predefined mirror drive.

11. Apparatus for processing data in data processing system including a redundant array of independent disk drives (RAID) comprising:

a plurality of data drives in the RAID;

a single predefined mirror drive in the RAID;

said single predefined mirror drive having a predefined capacity greater than or equal to a sum of the capacity of the plurality of data drives;

array controller means for operatively controlling operation of the RAID including;

means for writing data to multiple data drives in the RAID;

means for writing a mirror copy of said written data to said predefined mirror drive in the RAID;

means for reading data from said multiple data drives; and

means for identifying a failed one of said multiple data drive and for reading data from said predefined mirror drive.

12. Apparatus as recited in claim 11 further includes a write cache for temporarily storing write command data.