Dell PowerVault MD3220 - Manual (Page 117)

Configuration: Disk Groups and Virtual Disks 117
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.
CAUTION: Enclosure loss protection is not guaranteed if a physical disk has
already failed in the disk group. In this situation, losing access to an expansion
enclosure and consequently another physical disk in the disk group causes a
double physical disk failure and loss of data.
Enclosure loss protection is achieved when you create a disk group where all
of the physical disks that comprise the disk group are located in different
expansion enclosures. This distinction depends on the RAID level. If you
choose to create a disk group by using the Automatic method, the software
book.book Page 117 Tuesday, June 18, 2013 2:53 PM