Enclosure loss protection, See "enclosure loss – Dell POWERVAULT MD3620I User Manual

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Configuration: Disk Groups and Virtual Disks

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

attempts to choose physical disks that provide enclosure loss protection. If

you choose to create a disk group by using the Manual method, you must use

the criteria specified in Table 10-2.

Table 10-2. Criteria for Enclosure Loss Protection

RAID Level

Criteria for Enclosure Loss Protection

RAID level 5

or RAID level

6

Ensure that all the physical disks in the disk group are located in

different expansion enclosures.
Because a RAID level 5 requires a minimum of 3 physical disks,

enclosure loss protection cannot be achieved if your storage array has

less than 3 expansion enclosures.
Because a RAID level 6 requires a minimum of 5 physical disks,

enclosure loss protections cannot be achieved if your storage array has

less than 5 expansion enclosures.

book.book Page 134 Tuesday, June 18, 2013 3:09 PM

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