Creating custom pools

Create pools that have custom configurations by manually assigning arrays and RAID levels, and manually balancing spare drives and device adapter (DA) pairs.

1. Create a pair of pools that do not have arrays that are assigned to them by using the Create Pool Pair action on the Arrays by Pool page.
   The DS8000 Storage Management GUI automatically creates a pair of pools, which balances the workload between the two nodes.

   The Create Pool Pair page provides the options to create FB, CKD, and custom pool pairs. When you select Custom, you can change the size of the extent unit in the Extent unit field. You can also select the extent unit size when you assign an array to pool. However, when the array is already configured with an extent unit size, the drop-down menu is not available, and you are presented with a message.

   Note: DS8000 supports large (1 GB) and small (16 MB for FB, and 17.3 MB for CKD) extents.

   You need to consider several factors when you are deciding on whether to use large or small extents:

   • Small extents are required for effective use of thin provisioning and for functions such as FlashCopy and Safeguarded Copy. If you plan on using these functions immediately or in the lifetime of the storage system, you need to use small extents at least for any FlashCopy targets and for safeguarded backup capacity or thin provisioned volumes.
   • The use of small extents can result in limitations on the maximum raw and provisioned volume capacity that depend on the installed memory of the storage system. Refer to the Hardware overview for details about the maximum capacity for storage systems with large and small extents. If you expect to exceed the maximum usable or volume capacity that is supported by small extents, you should consider that use either large extents or a mix of large and small extents.
   • Using small extents will reduce the maximum sequential write performance for a single array by approximately 15%, although the maximum system throughput for larger systems with many arrays and HPFE enclosures is not reduced. This reduction is often offset in by the increased granularity of striping with small extents so that sequential reads and writes are more evenly spread over the arrays in a pool.
2. On the Arrays by Pool page, select the arrays to assign to the pools. To balance the arrays between the pools, consider the drive capacity, drive class, and DA pair assignments of the arrays.
   Important: Balance DA pairs between the pools to avoid bottlenecks.
3. To manually assign the arrays, select the Assign action.
4. In the Assign Arrays window, select the pool and the RAID level for the arrays.
5. After the arrays are assigned, check that spares and DA pairs are balanced between the two pools. To rebalance spares, click the Reassign action to move arrays from one pool to another.
   Note: You do not need to delete or reconfigure arrays when you reassign them to another pool.