Dell 34XX Using SSD Cache, Defragmenting a Disk Group, Enabling SSD Cache For a Virtual Disk

performance is maximized when a single I/O request is serviced with a single data stripe; use smaller values for the segment size. To change the segment size, run the following command:

set virtualDisk ([virtualDiskName] <wwid>) segmentSize=segmentSizeValue

where, segmentSizeValue is the new segment size you want to set. Valid segment size values are 8, 16, 32, 64, 128, 256, and 512. You can identify the virtual disk by name or World Wide Identifier (WWID) (see Set Virtual Disk).

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

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