Server Administrator Storage Management 8.3 User’s Guide

Setting The Patrol Read Mode

NOTE: This task is not supported on PERC hardware controllers running in HBA mode.

Does my controller support this feature? See Supported Features.

Patrol read identifies disk errors in order to avoid disk failures and data loss or corruption. The Set Patrol Read task is applicable only for disks used as virtual disks or hot spares.

The Set Patrol Read task runs in the background and corrects, when possible. When the Set Patrol Read mode is set to Auto, patrol read is initiated when the controller is idle for a period of time and when no other background tasks are active. In this scenario, the patrol read enhances the system performance as disk errors can be identified and corrected when there is not input/output activity on the disk.

The controller adjusts the amount of system resources dedicated for patrol read based on the amount of controller activity that is competing with the Patrol Read task. When the controller activity is high, fewer system resources are dedicated to the patrol read task.

Patrol Read does not run on a physical disk in the following circumstances:

• The physical disk is not included in a virtual disk or is assigned as a hot spare.
• The physical disk is included in a virtual disk that is currently undergoing one of the following:
  • Rebuild
  • Reconfiguration or reconstruction
  • Background initialization
  • Check consistency

In addition, the Patrol Read suspends during heavy I/O activity and resumes when the I/O is finished.