Users Guide

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.
To Set The Patrol Read Mode
Select the desired Patrol Read Mode option. The options available are:
● Auto — Initiates the Patrol Read task. After the task is complete, it automatically runs again within a specified period. For
example, on some controllers the Patrol Read runs every four hours and on other controllers, the Patrol Read runs every
seven days. The Patrol Read task runs continuously on the system starting again within the specified period after each
iteration of the task completes. If the system reboots while the Patrol Read task is running in Auto mode, the Patrol Read
restarts at zero percent (0%). When the Patrol Read task is set to Auto mode, you cannot start or stop the task. Auto
mode is the default setting.
NOTE:
For more information on how often the Patrol Read task runs when in Auto mode, see your controller
documentation.
● Manual — Enables you to start and stop the Patrol Read task using Start and Stop Patrol Read. Setting the mode to
Manual does not initiate the Patrol Read task. If the system reboots while Patrol Read is running in Manual mode, Patrol
Read does not restart.
● Disabled — Prevents the Patrol Read task from running on the system.
To Locate Set Patrol Read Mode In Storage Management
1. In the Server Administrator window, under the system tree, expand Storage to display the controller objects.
2. Select a controller object.
3. Click Information/Configuration on the controller Properties page.
4. Select Set Patrol Read mode from the Available Tasks drop-down menu.
5. Click Execute.
You can also locate this task from the Change Controller Properties drop-down menu.
Starting And Stopping Patrol Read
Does my controller support this feature? See Supported Features.
NOTE: The Patrol Read operation is not supported on solid-state drives (SSD).
NOTE: This task is not supported on PERC hardware controllers running in HBA mode.
When the Set Patrol Read mode is set to Manual, you can start the Patrol Read task or stop the task when it is running.
There are certain conditions under which the Patrol Read task cannot be run.
Controllers
71