Enclosure loss protection – Dell PowerVault MD3220 User Manual

Page 117

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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

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