Easy Tier considerations and limitations

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When you plan for volume migration, it is important to consider how Easy Tier® functions with storage configurations, and recognize its limitations.

Migration considerations

The following information might be helpful in using Easy Tier with your DS8000® storage system:

  • You cannot initiate a volume migration on a volume that is being migrated. The first migration must complete first.
  • You cannot initiate, pause, resume, or cancel migration on selected volumes that are aliases or virtual volumes.
  • You cannot migrate volumes from one extent pool to another or change the extent allocation method unless the Easy Tier feature is installed on the storage system.
  • Volume migration is supported for standard, auxiliary, and ESE volumes.
  • If you specify a different extent allocation method for a volume, the new extent allocation method takes effect immediately.
  • A volume that is being migrated cannot be expanded and a volume that is being expanded cannot be migrated.
  • When a volume is migrated out of an extent pool that is managed with Easy Tier, or when Easy Tier is no longer installed, the DS8A00 disables Easy Tier and no longer automatically relocates high activity I/O data on that volume between storage devices.

Limitations

The following limitations apply to the use of Easy Tier:

  • You cannot merge two extent pools if you selected an extent pool that contains volumes that are being migrated.
  • It might be helpful to know that some basic characteristics of Easy Tier might limit the applicability for your generalized workloads. The granularity of the extent that can be relocated within the hierarchy is large (1 GB). Additionally, the time period over which the monitoring is analyzed is continuous, and long (24 hours). Therefore, some workloads might have hot spots, but when considered over the range of the relocation size, they do not appear, on average, to be hot. Also, some workloads might have hot spots for short periods of time, but when considered over the duration of the analysis window, the hot spots do not appear, on average, to be hot.