Dell PowerEdge RAID Controller S100 - Manual (Page 87)

Appendix B 87
Rescanning Physical Disks for Changes in State
The physical disk information displayed at the PERC Virtual Disk
Management utility is the state of the physical disks when they were last
scanned. If a rescan has not been performed, the information displayed is the
state of the physical disks at boot time.
Every time a physical disk is connected or disconnected while online, a rescan
is performed. A rescan is automatically performed when Dell OpenManage
Server Administrator Storage Management detects that a physical disk has
been added or removed.
Dedicated Hot Spares
A dedicated hot spare is a backup physical disk for the redundant virtual disk
to which it is assigned. The physical disk that is used as a dedicated hot spare
cannot be a member of an existing virtual disk. When the hot spare is
activated, it becomes the receptacle for the data from the failed physical disk
member of the volume, without interrupting the system or requiring your
intervention.
A dedicated hot spare can be assigned to any redundant virtual disk, and up to
four hot spares can be assigned to a virtual disk. However, a dedicated hot
spare cannot be assigned while a task is running on the virtual disk.
A global hot spare can be assigned when a virtual disk is created in the PERC
Virtual Disk Management utility. A global hot spare can be added at any time
when Storage Management is used.
If there is enough space available on the dedicated hot spare, and a disk
failure occurs, the rebuild process for the virtual disk starts automatically.
Dedicated hot spare assignments do not apply to a non-redundant virtual
disk.
NOTE: A virtual disk is marked Failed or Degraded if a physical disk reports a Failed
state, or if the SAS/SATA cable to the physical disk or power cable is disconnected.
A dedicated hot spare is often preferred to a global hot spare, especially for
critical data. This is because a dedicated hot spare guarantees that the virtual
disk has a backup physical disk assigned exclusively to it in case of a failure.
For additional information, see "Managing Global Hot Spares" on page 56.
A5_bk0.book Page 87 Thursday, February 10, 2011 8:34 PM