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118 Configuration: Disk Groups and Virtual Disks
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 9-2.
Table 9-2. 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.
RAID level 1 Ensure that each physical disk in a mirrored pair is located in a
different expansion enclosure. This enables you to have more than
two physical disks in the disk group within the same expansion
enclosure.
For example, if you are creating a six physical disk, disk group (3-
mirrored pairs), you can achieve enclosure loss protection with only
two expansion enclosures by specifying that the physical disk in each
mirrored pair are located in separate expansion enclosures. For
example:
• Mirror pair 1—Physical disk in enclosure 1, slot 1 and physical disk in
enclosure 2, slot 1.
• Mirror pair 2—Physical disk in enclosure 1, slot 2 and physical disk in
enclosure 2, slot 2.
• Mirror pair 3—Physical disk in enclosure 1, slot 3 and physical disk in
enclosure 2,slot 3.
Because a RAID level 1 disk group requires a minimum of two physical
disks, enclosure loss protections cannot be achieved if your storage
array has less than two expansion enclosures.
RAID level 0 Because RAID level 0 does not have consistency, you cannot achieve
enclosure loss protection.
book.book Page 118 Tuesday, September 27, 2011 3:25 PM