Data redundancy and recovery protection

• US 5,101,492 A
• Filed: 11/03/1989
• Issued: 03/31/1992
• Est. Priority Date: 11/03/1989
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Compaq Computer Corporation (HP Inc.)
• Inventors: Neufeld, E. David, Schultz, Stephen M., Schmenk, David S., Flower, David L.
• Primary Examiner(s): ATKINSON, CHARLES
• Application Number:
  US07/431,741
• Time in Patent Office: 879 Days
• Field of Search: 371/10.1, 371/10.2, 371/40.1, 364/268.3, 364/268.5, 364/268.9, 364/269.2, 395/575
• US Class Current: 714/6.32
• CPC Class Codes: G06F 11/1092 Rebuilding, e.g. when physically replacing a failing disk
• CPC Class Codes: G11B 20/1833 by adding special lists or symbols to the coded information G11B20/1806, G11B20/1866 take precedence
• CPC Class Codes: G11C 29/74 using duplex memories, i.e. using dual copies

Abstract

A method for detecting the presence of a replacement disk in a fault tolerant, intelligent mass storage disk array subsystem having a microprocessor based controller in a personal computer system and rebuilding the replacement disk independent of the computer system processor. The method calls for the microprocessor controller to run a disk array check at system powerup or at specified intervals to detect the existence of a replacement drive. The microprocessor then builds a series of disk drive commands which attempt to read every sector on the replacement disk. The read commands will return a null data read, indicating that the sector must be restored. The microprocessor controller converts the replacement read commands for all sectors on the replacement disk to write-restore commands. The microprocessor executes the write commands and restores the data to the replacement drive.

Claims

1. For use with a computer system having a fault tolerant, intelligent mass storage disk array subsystem, the disk subsystem having a microprocessor based controller, a method for rebuilding a replacement disk drive within the array without system processor supervision or suspension of system operations comprising:

reading disk array and disk drive status information and fault tolerance mode for the disk array from reserved sectors on all disk drives within the drive array;

reading disk array and disk drive status information and fault tolerance mode for the disk array from reserved sectors on all disk drives within the drive array;

determining if one or more of the drives in the array has been replaced from disk drive status information;

reading all sectors on the replacement drive, thereby causing a failed sector read to occur when attempting to read the replacement drive sectors, indicating a sector to be restored;

generating rebuild commands for the replacement disk by writing to each failed sector utilizing the active fault tolerance mode;

queueing the rebuild commands; and

executing the rebuild commands by the microprocessor controller independent of the computer system processor, thereby restoring data to the replacement disk drive.

2. The method of claim 1, wherein determining if one or more of the disk drives in the disk array is a replacement drive includes running a drive array check program by the microprocessor controller at each computer system power-up.

3. The method of claim 1, wherein determining if one or more of the disk drives in the disk array is a replacement drive includes running a drive array check program at periodic intervals by the microprocessor controller.

4. The method of claim 2, wherein determining if one or more of the disk drives in the disk array is a replacement drive includes comprising individual disk drive information to a disk array configuration template maintained by the microprocessor controller.

5. The method of claim 3, wherein determining if one or more of the disk drives in the disk array is a replacement drive includes comparing individual disk drive information to a disk array configuration template maintained by the microprocessor controller.

6. The method of claim 1, wherein reading all sectors on the replaced drive includes creating an information packet for each sector on the drive, the information packet including drive array and disk drive information from a disk array configuration template, a read command and physical drive parameters indicating the location of the sector to be read.

7. The method of claim 6, wherein generating rebuild commands includes:

creating a rebuild header command, including information from the drive array and disk drive configuration template, the fault tolerance mode and instructions to activate the fault recovery mode;

changing the read command for each sector in the replacement drive to a write command; and

linking all of the write commands to the rebuild command header.

8. The method of claim 7, wherein the method of restoring data to the replacement disk drive includes writing the restored data to the replacement disk from a mirror data disk.

9. The method of claim 7, wherein the method of restoring data to the replacement disk drive includes, generating the restored data utilizing an XOR parity technique from data on the remaining disks within the array.

10. The method of claim 9, wherein the method of generating the restored data includes generating the restored data utilizing a dedicated XOR parity engine within the disk array subsystem.