System and method for reducing unrecoverable media errors in a disk subsystem

• US 7,275,179 B1
• Filed: 04/24/2003
• Issued: 09/25/2007
• Est. Priority Date: 04/24/2003
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Inventors: Coatney, Douglas W.
• Primary Examiner(s): Baderman; Scott
• Assistant Examiner(s): LOHN, JOSHUA A
• Application Number:
  US10/422,531
• Time in Patent Office: 1,615 Days
• Field of Search: 714/5, 714/6, 714/7, 714/8, 714/42, 714/770
• US Class Current: 714/6.32
• CPC Class Codes: G06F 11/1084 Degraded mode, e.g. caused by single or multiple storage removals or disk failures

Abstract

A system and method for reducing unrecoverable errors in a disk drive by under-taking an aggressive reassignment of slow-reading or currently recoverable-but-erroneous sectors to the spares pool is provided. A recovered error is treated by the system operating system as a fatal error and thereby the sectors involved are reassigned to the spares pool immediately. Reassignment is recommended by a reassignment utility at the disk interface level, which passes a status up to the RAID subsystem by which reassignment is performed. In order to prevent a double-disk panic, the RAID subsystem is instructed to ignore reassignment recommendations of this type (e.g. reassignment of recoverable errors) if the RAID group is currently operating in a degraded state. However, if the RAID group is undegraded, then immediate assignment of the sectors encountering the recoverable error is undertaken.

Claims

1. A method for handling a disk error, comprising:

receiving, in response to an I/O operation, a status signal indicating a disk error;

determining if a RAID group containing the disk is in a degraded state;

if the RAID group is not in the degraded state, reassigning the I/O operation to a spare sector; and

if the RAID group is in the degraded state;

not reassigning the I/O operation to the spare sector, and

storing the I/O operation in a log to reassign to the spare sector at a future time.

2. The method of claim 1, wherein the RAID group is in the degraded state after a disk failure occurs to another disk within the RAID group but before reconstruction has completed of the disk failure.

3. The method as set forth in claim 1 wherein the spare disk sector is one of a plurality of spare disk sectors included in a spares pool on the disk and is mapped via a defect list associated with the disk.

4. An apparatus for handling a disk error, comprising:

means for receiving, in response to an I/O operation, a status signal indicating a disk error;

means for determining if a RAID group containing the disk is in a degraded state;

if the RAID group is not in the degraded state, means for reassigning the I/O operation to a spare sector; and

if the RAID group is in the degraded state;

means for not reassigning the I/O operation to the spare sector; and

means for storing the I/O operation in a log to reassign to the spare sector at a future time.

5. The apparatus of claim 4, wherein the RAID group is in the degraded state after a disk failure occurs to another disk within the RAID group but before reconstruction has completed of the disk failure.

6. A system for handling a disk error, comprising:

a storage adapter for receiving, in response to an I/O operation, a status signal indicating a disk error;

a mechanism in the storage layer for determining if a RAID group containing the disk is in a degraded state, and if the RAID group is not in the degraded state, reassigning the I/O operation to a spare sector; and

if the RAID group is in the degraded state, the mechanism is further configured to;

not reassign the I/O operation to the spare sector, and

store the I/O operation in a log to reassign to the spare sector at a future time.

7. The system of claim 6, wherein the RAID group is in the degraded state after a disk failure occurs to another disk within the RAID group but before reconstruction has completed of the disk failure.

8. The system as set forth in claim 6 wherein the spare sector is one of a plurality of spare sectors included in a spares pool on the storage device and is mapped via a defect list associated with the storage device.

9. A computer readable media, comprising:

the computer readable media containing instructions for execution on a processor for the practice of the method for handling a disk error, comprising;

receiving, in response to an I/O operation, a status signal indicating a disk error;

determining if a RAID group containing the disk is in a degraded state; and

if the RAID group is not in the degraded state, reassigning the I/O operation to a spare sector

if the RAID group is in the degraded state;

not reassigning the I/O operation to the spare sector, and

storing the I/O operation in a log to reassign to the spare sector at a further time.

10. The computer-readable medium as set forth in claim 9 wherein the spare disk sector is one of a plurality of sectors included in a spares pool on the disk and is mapped via a defect list associated with the disk.