Dell PowerVault ME5 Series Administrator's Guide

SSDs

The use of SSDs (solid-state drives) can greatly enhance the performance of a system. Since the SSDs do not have moving parts, data that is random in nature can be accessed much faster.

You can use SSDs for virtual disk groups in a system that contains only SSDs, or in a system that uses SSDs in combination with spinning disks. When combined with virtual disk groups that consist of other classes of disks, improved read and write performance is possible through automated tiered storage. Alternatively, you can use one or two SSDs in read-cache disk groups to increase read performance for pools without a Performance tier. The application workload of a system determines the percentage of SSDs of the total disk capacity that is needed for best performance.

The use of SSDs may also greatly enhance the performance of a linear system for the same reasons they benefit a virtual system. You can use SSDs in combination with spinning disks. The application workload of a system determines the percentage of SSDs of the total disk capacity that is needed for best performance.

Follow these recommendations for using SSDs and spinning disks:

• If the first disk group is provisioned with SSDs, then the system will expect to be provisioned as an all-flash array and allow only SSDs to be used in all other disk groups.
• If the first disk group is provisioned with spinning disks, then the system can only be provisioned to use spinning disks in virtual disk groups and use SSDs as read cache.
• If the first disk group is provisioned with spinning disks or SSDs, then the system can be provisioned to use spinning disks in virtual disk groups and use SSDs either in virtual disk groups or as read cache.