Dell PowerVault MD3820f - Manual (Page 28)

If a redundant RAID controller module fails with an existing disk group process, the process on the failed
controller is transferred to the peer controller. A transferred process is placed in a suspended state if
there is an active disk group process on the peer controller. The suspended processes are resumed when
the active process on the peer controller completes or is stopped.
NOTE: If you try to start a disk group process on a controller that does not have an existing active
process, the start attempt fails if the first virtual disk in the disk group is owned by the other
controller and there is an active process on the other controller.
RAID Background Operations Priority
The storage array supports a common configurable priority for the following RAID operations:
• Background initialization
• Rebuild
• Copy back
• Virtual disk capacity expansion
• Raid level migration
• Segment size migration
• Disk group expansion
• Disk group defragmentation
The priority of each of these operations can be changed to address performance requirements of the
environment in which the operations are to be executed.
NOTE: Setting a high priority level impacts storage array performance. It is not advisable to set
priority levels at the maximum level. Priority must also be assessed in terms of impact to host server
access and time to complete an operation. For example, the longer a rebuild of a degraded virtual
disk takes, the greater the risk for potential secondary disk failure.
Virtual Disk Migration And Disk Roaming
Virtual disk migration is moving a virtual disk or a hot spare from one array to another by detaching the
physical disks and re-attaching them to the new array. Disk roaming is moving a physical disk from one
slot to another on the same array.
Disk Migration
You can move virtual disks from one array to another without taking the target array offline. However, the
disk group being migrated must be offline prior to performing the disk migration. If the disk group is not
offline prior to migration, the source array holding the physical and virtual disks within the disk group
marks them as missing. However, the disk groups themselves migrate to the target array.
An array can import a virtual disk only if it is in an optimal state. You can move virtual disks that are part of
a disk group only if all members of the disk group are being migrated. The virtual disks automatically
become available after the target array has finished importing all the disks in the disk group.
When you migrate a physical disk or a disk group from:
• One MD storage array to another MD storage array of the same type (for example, from an MD3460
storage array to another MD3460 storage array), the MD storage array you migrate to, recognizes any
data structures and/or metadata you had in place on the migrating MD storage array.
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