Dell PowerEdge RAID Controller 5i - Manual (Page 24)

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PERC 5 Features
Physical Disk Hot Swapping
Hot swapping is the manual substitution of a replacement unit in a disk subsystem for a defective one,
where the substitution can be performed while the subsystem is running (performing its normal functions).
NOTE:
The backplane or enclosure must support hot swapping in order for the PERC 5 controllers to support
hot swapping.
NOTE:
Ensure that SAS drives are replaced with SAS drives and SATA drives are replaced with SATA drives.
NOTE:
While swapping a disk, ensure that the new disk is of equal or greater capacity than the disk that is
being replaced.
Failed Physical Disk Detection
The firmware automatically detects and rebuilds failed physical disks. Automatic rebuilds can be performed
transparently with hot spares. If you have configured hot spares, the controllers automatically try to use
them to rebuild failed physical disks.
Patrol Read
The Patrol Read function is designed as a preventive measure that includes review of your system for
possible physical disk errors that could lead to physical disk failure and damage data integrity. The Patrol
Read operation can find and possibly resolve any potential problem with physical disks prior to host
access. This can enhance overall system performance because error recovery during a normal I/O operation
may not be necessary. You can use the storage management application to perform Patrol Read functions.
Patrol Read Behavior
The following is an overview of Patrol Read behavior:
1 Patrol Read runs on all disks on the controller that are configured as part of a virtual disk including hot
spares. Patrol Read does not run on unconfigured physical disks. Unconfigured disks are those that are
not part of a virtual disk or are in a ready state.
2 Patrol Read adjusts the amount of controller resources dedicated to Patrol Read operations based on
outstanding disk I/O. For example, if the system is busy processing I/O operation, then Patrol Read will
use fewer resources to allow the I/O to take a higher priority.
3 Patrol Read operates on all configured physical disks on the controller and there is no method to
deselect disks.
4 In a Patrol Read iteration, Patrol Read will restart from zero percent if in Auto mode. In Manual mode,
Patrol Read does not restart on a reboot. Use Manual mode if you have selected a window of time
dedicated to running Patrol Read.
Dell_PERC5_UG.book Page 22 Tuesday, February 13, 2007 6:02 PM