Dell PowerVault MD3000, Hardware Owner'S Manual

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36
Using Your RAID Enclosure
NOTE:
If you try to start a disk group process on a controller that does not have an existing active process, the
start attempt will fail 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 controller 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, and 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 will impact storage array performance. It is not advisable to set priority levels at
the maximum level. Priority should also be assessed in terms of impact to host 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
will mark them as missing. However, the disk groups themselves will still be migrated 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 MD3000 array to another, the MD3000 you
migrate to will recognize any data structures and/or metadata you had in place on the migrating
MD3000. However, if you are migrating from another storage array, the MD3000 array will not recognize
the migrating metadata. In this case, the RAID controller will initialize the physical disks and mark them
as unconfigured capacity.
Disk Roaming
Moving physical disks within an array is called disk roaming . The RAID controller module automatically
recognizes the relocated physical disks and logically places them in the proper virtual disks that are part
of the disk group. Disk roaming is permitted whether the RAID controller module is either online or
powered off.
NOTE:
The disk group must be offline before moving the physical disks.