Dell PowerVault MD3200i - Manual (Page 126)

126 Configuration: Disk Groups and Virtual Disks
Hot Spare Drive Protection
You can use a hot spare physical disk for additional data protection from
physical disk failures that occur in a RAID level 1, or RAID level 5 disk group.
If the hot spare physical disk is available when a physical disk fails, the RAID
controller module uses redundancy data to reconstruct the data from the
failed physical disk to the hot spare physical disk. When you have physically
replaced the failed physical disk, a copyback operation occurs from the hot
spare physical disk to the replaced physical disk.
If there are secure disk groups and security capable disk groups in the storage
array, the hot spare physical disk must match the security capability of the
disk group. For example, a non-security capable physical disk cannot be used
as a hot spare for a secure disk group.
NOTE: For a security capable disk group, security capable hot spare physical disks
are preferred. If security capable physical disks are not available, non-security
capable physical disks may be used as hot spare physical disks. To ensure that the
disk group is retained as security capable, the non-security capable hot spare
physical disk must be replaced with a security capable physical disk.
If you select a security capable physical disk as hot spare for a non-secure disk
group, a dialog box is displayed indicating that a security capable physical disk
is being used as a hot spare for a non-secure disk group.
The availability of enclosure loss protection for a disk group depends on the
location of the physical disks that comprise the disk group. The enclosure loss
protection may be lost because of a failed physical disk and location of the hot
spare physical disk. To make sure that enclosure loss protection is not
affected, you must replace a failed physical disk to initiate the copyback
process.
The virtual disk remains online and accessible while you are replacing the
failed physical disk, because the hot spare physical disk is automatically
substituted for the failed physical disk.
Enclosure Loss Protection
Enclosure loss protection is an attribute of a disk group. Enclosure loss
protection guarantees accessibility to the data on the virtual disks in a disk
group if a total loss of communication occurs with a single expansion
enclosure. An example of total loss of communication may be loss of power to
the expansion enclosure or failure of both RAID controller modules.
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