A SMART failure is also referred to as a predicted failure. There are numerous factors that relate to predicted physical
disk failures, such as a bearing failure, a broken read/write head, and changes in spin-up rate. In addition, there are
factors related to read/write surface failure, such as seek error rate and excessive bad sectors.
NOTE: For detailed information on SCSI interface specifications, see t10.org.
Patrol Read
The Patrol Read feature is designed as a preventive measure to ensure physical disk health and data integrity. Patrol
Read scans for and resolves potential problems on configured physical disks. The Dell Chassis Management Controller
(CMC) can be used to start and control the features of Patrol Read.
The following is an overview of Patrol Read:
•
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 physical disks that are not part of a virtual disk or are in Ready state.
•
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 uses fewer
resources to allow the I/O to take a higher priority.
•
Patrol Read does not run on disks involved in any of the following operations:
–
Rebuild
–
Replace Member
–
Full or Background Initialization
–
Consistency Check (CC)
NOTE: By default, Patrol Read automatically runs every seven days on configured SAS hard drives. Patrol
Read is not necessary on SSD and is disabled by default.
For more information on Patrol Read, see the Dell OpenManage documentation at dell.com/support/manuals.
Physical Disk Failure Detection
Failed physical disks are detected and rebuilds automatically start to new disks that are inserted into the same slot.
Automatic rebuilds can also happen transparently with hot spares. If you have configured hot spares, the controllers
automatically try to use them to rebuild failed physical disks.
Physical Disk Hot Swapping
NOTE: Shared PERC 8 supports hot swapping, however this should only be implemented for unconfigured or failed
drives.
Hot swapping is the manual replacement of a disk while the Shared PERC 8 card is online and performing the normal
functions. The following requirements must be fulfilled before performing a hot swap of a physical disk:
•
The replacement disk must be of the same protocol and disk technology. For example, only a SAS hard drive can
replace a SAS hard drive.
•
The replacement disk must be of equal or greater capacity than the one it is replacing.
Auto Replacement Of A Virtual Disk Member And Revertible Hot Spares
The automatic Replace Member functionality allows a previously commissioned hot spare to be reverted to a usable hot
spare. When a disk failure occurs within a virtual disk, an assigned hot spare (dedicated or global) is commissioned and
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