Drawer Loss Protection - Dell PowerVault MD3260i Administrator's Manual

RAID Level Criteria for Enclosure Loss Protection
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:
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 4. Drawer Loss Protection Requirements for Different RAID Levels
RAID Level
RAID Level 6
RAID Level 5
RAID Level 1 and RAID
Level 10
• 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.
Drawer Loss Protection Requirements
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 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.
RAID Level 1 requires a minimum of two physical disks. Make sure that each physical disk in
a remotely replicated pair is located in a different drawer. By locating each physical disk in
a different drawer, you can have more than two physical disks of the disk group within the
same drawer. For example, if you create a RAID Level 1 disk group with six physical disks
(three replicated pairs), you can achieve the drawer loss protection for the disk group with
only two drawers as shown in this example: Six-physical disk RAID Level 1 disk group:
75