Drawer loss protection – Dell PowerVault MD3820f User Manual
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RAID Level
Criteria for Enclosure Loss Protection
Because a RAID level 5 requires a minimum of three physical disks, enclosure loss
protections cannot be achieved if your storage array has less than three expansion
enclosures. Because a RAID level 6 requires a minimum of five physical disks,
enclosure loss protections cannot be achieved if your storage array has less than
five 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 (three-mirrored
pairs), you could 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. This example shows this concept:
• 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.
Drawer Loss Protection
In expansion enclosures that contain drawer-based physical disks, a drawer failure can prevent access to
data on the virtual disks of a disk group.
Drawer loss protection for a disk group is based on the location of the physical disks that comprise the
disk group. In the event of a single drawer failure, data on the virtual disks in a disk group will remain
accessible if drawer loss protection configuration is followed. In such as case, if a drawer fails and the disk
group is protected, the disk group changes to Degraded status and the data remains accessible.
To configure your storage for drawer loss protection, make sure that physical disks that are part of a disk
group are located in different drawers with respect to their RAID levels, as shown in the following table.
Table 5. Drawer Loss Protection Requirements for Different RAID Levels
RAID Level
Drawer Loss Protection Requirements
RAID Level 6
RAID Level 6 requires a minimum of five physical disks. Place all of the physical
disks in different drawers or place a maximum of two physical disks in the same
drawer and the remaining physical disks in different drawers.
RAID Level 5
RAID Level 5 requires a minimum of three physical disks. Place all of the physical
disks in different drawers for a RAID Level 5 disk group. Drawer loss protection
cannot be achieved for RAID Level 5 if more than one physical disk is placed in
the same drawer.
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