Users Guide
Dedicated Hot Spare Considerations
The following considerations apply to dedicated hot spares:
l Considerations for RAID 10, RAID 50, and RAID 60. If you have created a RAID 10 or RAID 50 virtual disk that does not fully consume its member
physical disks, then you will not be able to assign a dedicated hot spare to the RAID 10 or RAID 50 virtual disk. Storage Management does not allow you
to create RAID 10 and RAID 50 virtual disks from partial physical disks. You will therefore not encounter this situation if you are using Storage
Management to create your virtual disks. If, however, the RAID 10 or 50 virtual disk was created using another application and if it does contain partial
physical disks, then you will not be able to assign a dedicated hot spare to the virtual disk.
l Considerations for Multiple Dedicated Hot Spares. From Storage Management version 3.1 onwards, Storage Management enables you to assign more
than one dedicated hot spare to a virtual disk.
Physical Disk State, Alert Messages and Hot Spares on PERC 3/SC, 3/DC, 3/QC, 4/SC,
4/DC, 4e/DC, 4/Di, 4e/Si, 4e/Di, and CERC ATA100/4ch Controllers
If you have a hot spare assigned to a virtual disk and a physical disk in the virtual disk fails, the failed physical disk may change from Online state to Ready
state without displaying a Failed state. This occurs when the hot spare is activated before the physical disk is able to report the Failed state. Because the
Failed state is not reported, the "Device failed: physical disk" event 2048 is not generated.
When the hot spare is activated, the hot spare displays the "Rebuilding" state. If you review the event log and identify a "rebuilding" event such as 2064 or
2065, you can assume that a physical disk has failed.
For information on Alert Messages, see the Dell OpenManage Server Administrator Messages Reference Guide on the Dell Support website at
support.dell.com/manuals.
Considerations for Hot Spares on PERC 3/Si, 3/Di, CERC SATA1.5/6ch, S100, and
S300 Controllers
For the PERC 3/Si, 3/Di, CERC SATA1.5/6ch, S100, and S300 controllers, a hot spare is assigned to a virtual disk. When a physical disk fails, only the portion of
the physical disk containing the virtual disk is rebuilt onto the hot spare. Data or space on the physical disk not included in the virtual disk will not be rebuilt.
On the PERC 3/Si, 3/Di, CERC SATA1.5/6ch, S100, and S300 controllers, individual physical disks may be included in more than one virtual disk. (Assigning a
portion of a physical disk to a virtual disk does not preclude the remaining portion of the physical disk from being used by other virtual disks.) Only the virtual
disks to which the hot spare is assigned will be rebuilt. When using Storage Management, a disk that is assigned as a hot spare on a PERC 3/Si, 3/Di, CERC
SATA1.5/6ch, S100, and S300 controller cannot be used as a member of a virtual disk.
Size Requirements for Global Hot Spares on PERC 3/Si, 3/Di, CERC SATA1.5/6ch, S100, and
S300 Controllers
When assigning a physical disk as a global hot spare on a PERC 3/Si, 3/Di, CERC SATA1.5/6ch, S100, and S300 controllers, the physical disk should be as large
or larger than the largest physical disk on the controller.
Dedicated Hot Spare Considerations on PERC 3/Si, 3/Di, and CERC SATA1.5/6ch Controllers
You can assign the same dedicated hot spare to more than one virtual disk. In this case, the hot spare attempts to rebuild all portions of redundant virtual
disks that reside on a failed physical disk. To increase the likelihood that the hot spare is able to rebuild all virtual disks, you should do the following:
1. Create virtual disks that share the same set of physical disks.
2. Only assign dedicated hot spares to those virtual disks that share the same set of physical disks.
3. Assign a hot spare that is big enough to rebuild the largest physical disk in the virtual disk. For example, if the virtual disk is using physical disks that are
20 MB, 30 MB, and 50 MB, then the hot spare needs to be 50 MB or larger.
After the hot spare is activated to rebuild a particular virtual disk, it is no longer available for rebuilding other virtual disks should an additional physical disk
fail. For this reason, when a hot spare is activated it is automatically unassigned from the remaining virtual disks. To maintain data protection, you will need to
add a new hot spare and assign it to the other virtual disks.
Global Hot Spare Considerations on a SAS 6/iR
NOTE: For H700 and H800 controllers, you can assign a dedicated hot spare to RAID 10, RAID 50, and RAID 60.
NOTE: This feature is applicable only on PERC 5 and PERC 6 family of controllers.
NOTE: When using the BIOS on a PERC 3/Si, 3/Di, or CERC SATA1.5/6ch controller, it may be possible to create a hot spare from a physical disk that is
also used in a virtual disk. To avoid confusion and maximize data protection, Storage Management does not allow a physical disk to be both a hot spare
and a member of a virtual disk. When assigning a hot spare, Storage Management displays the physical disks that are not being used by a virtual disk.
NOTE: The "Assign and Unassign Dedicated Hot Spare" command is not available on the CERC SATA1.5/2s controller.