Drawer loss protection is an attribute of volume groups and disk pools. Drawer loss protection guarantees accessibility to the data on the volumes in a volume group or disk pool if a total loss of communication occurs with a single drawer in a drive tray. An example of total loss of communication might be failure of an internal component within the drawer.
Attention: Drawer loss protection is not guaranteed if a drive has already failed in the volume group or disk pool. In this situation, losing access to a drawer and consequently another drive in the volume group or disk pool causes loss of data.
Criteria for drawer loss protection
- Disk pools
- Drawer Loss Protection is achieved when the disk pool includes drives from all five drawers and there are an equal number of drives in each drawer. A 60-drive tray can achieve drawer loss protection when the disk pool contains 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 drives.
- If the storage array has five or more drawers and the maximum number of eligible drives is not evenly distributed, you cannot create disk pools using the Automatic Configuration method. Instead, use the
menu option to create disk pools that contain drives eligible for drawer loss protection.
- Volume groups
- The criteria for drawer loss protection is dependent on RAID level as described in the following table. If you choose to create a volume group by using the Automatic method, the system attempts to choose drives that provide drawer loss protection. If you choose to create a volume group by using the Manual method, you must use the criteria that are specified in the following table.
Level |
Criteria for Drawer Loss Protection |
Minimum number of drawers required |
Disk Pool |
The disk pool includes drives from all five drawers and there are an equal number of drives in each drawer. A 60-drive tray can achieve Drawer Loss Protection when the disk pool contains 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 drives. |
5 |
RAID 6 |
The volume group contains no more than two drives in a single drawer. |
3 |
RAID 3 or RAID 5 |
Each drive in the volume group is located in a separate drawer. |
3 |
RAID 1 |
Each drive in a mirrored pair must be located in a separate drawer. |
2 |
RAID 0 |
Cannot achieve Drawer Loss Protection. |
Not applicable |