Dell PowerVault MD3200i Owner's Manual page 127

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 Ensure that all the physical disks in the disk group are located in
or RAID level different expansion enclosures.
6
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.
Configuration: Disk Groups and Virtual Disks
127