PRIMECLUSTER Global Disk Services Configuration and Administration Guide 4.1 (Solaris(TM) Operating System)

1.2.2 Hot Spare

Overview

"hot spare" is a feature that realizes automatic mirroring recovery using spare disks in the event of mirrored disk failure.

[Figure: Hot Spare]

Spare Disk Automatic Connection

If an I/O error occurs in a disk connected to a mirror group, a spare disk is automatically connected to the mirror group. Subsequently, synchronization copying for the spare disk takes place and the mirroring status will be restored.

Spare Disk Automatic Disconnection

After the disk where an I/O error occurred is recovered, the spare disk is automatically disconnected from the mirror group. For example, if disk failure causes an I/O error and a spare disk is automatically connected, after the failed disk is swapped with another disk and synchronization copying to the new disk is complete, the spare disk will automatically be disconnected.

Hot Spare Mode (Spare Disk Selection Mode)

A spare disk automatically connected in the event of I/O error in a mirrored disk is selected from spare disks that are registered with the failed disk's class. There are two modes of selecting spare disks: external mode and internal mode.

• External Mode (Default)

  If an I/O error occurs in a disk of a disk array unit, this method selects a spare disk that belongs to a different disk case from that of the failed disk.

  If an I/O error occurs in a disk irrelevant to a disk array unit (such as an internal disk), it selects a spare disk that is connected to a controller different from that the failed disk is connected to first.

  When no applicable unconnected spare disk is found there, a spare disk that belongs to the same disk case or is connected to the same controller as that of the disk with the I/O error is selected.

  Features:
  If an I/O error occurs in a disk, the I/O cable of the disk case may cause an error, the entire disk case may be down, or the controller may have a breakdown. By searching for a spare disk starting from a different disk case or controller from that of a disk with an I/O error, a normal spare disk can promptly be found and early mirroring recovery becomes possible.
  

  [Figure: Hot Spare in External mode]

  

  
  

• Internal Mode

  If an I/O error occurs in a disk of a disk array unit, this method selects a spare disk that belongs to the same disk case as that of the failed disk.

  If an I/O error occurs in a disk irrelevant to a disk array unit (such as an internal disk), it selects a spare disk that is connected to the same controller as that of the failed disk.

  When no applicable unconnected spare disk is found there, spare disk automatic connection is not performed.

  Features:
  A configuration that mirrors disks belonging to different disk unit cases or connected to different controllers is the configuration with high-availability, which secures continuous operations even if one of the disk cases or controllers fails. By selecting a spare disk that belongs to the same disk case or is connected to the same controller as that of the disk with an I/O error, the configuration with high-availability can be maintained.

  [Figure: Hot Spare in Internal Mode]

  

  
  

Points of Concern for Hot Spare
See "Hot Spare."