Dell PowerVault MD3260i - Manual (Page 112)

Defragmenting A Disk Group
When you defragment a disk group, you consolidate the free capacity in the disk group into one contiguous area.
Defragmentation does not change the way in which the data is stored on the virtual disks. As an example, consider a
disk group with five virtual disks. If you delete virtual disks 1 and 3, your disk group is configured in the following manner:
space, virtual disk 2, space, virtual disk 4, virtual disk 5, original unused space
When you defragment this group, the space (free capacity) is consolidated into one contiguous location after the virtual
disks. After being defragmented, the disk group is:
virtual disk 2, virtual disk 4, virtual disk 5, consolidated unused space
To defragment a disk group, run the following command:
start diskGroup [diskGroupNumber] defragment
where, diskGroupNumber is the identifier for the disk group.
NOTE: Defragmenting a disk group starts a long-running operation.
Using SSD Cache
If you are using solid-state disks (SSDs) in your storage array, you can configure SSD cache and model potential
workload throughput improvements, including cache hit percentage and average response time. SSD cache improves
read-only performance by logically grouping SSDs together to provide secondary cache to the primary cache in the
RAID controller module memory.
Enabling SSD Cache For A Virtual Disk
This set virtualDisk command turns SSD caching on or off on a standard virtual disk, snapshot virtual disk or a
consistency group snapshot virtual disk. Set the ssdCacheEnabled parameter to TRUE to enable SSD caching.
For standard virtual disks:
set virtualDisk ["virtualdiskName"]
ssdCacheEnabled=TRUE
For snapshot virtual disks:
set snapVirtualDisk ["virtualdiskName"]
ssdCacheEnabled=TRUE
For a consistency group snapshot virtual disk:
set cgSnapVirtualDisk ["cgSnapshotVirtualDisk"]
ssdCacheEnabled=TRUE
When you turn off SSD caching for a virtual disk, cache contents is purged. You can turn on SSD caching for only one
virtual disk per command.
Creating SSD Cache
To create ssdCache command SSD read cache:
create ssdCache userLabel="ssdCacheName"
physicalDisks=(enclosureID1,drawerID1,slotID1 ...
enclosureIDn,drawerIDn,slotIDn)
[updateExistingVirtualDisks=(TRUE|FALSE)]
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