IBM Storwize V5010 Manual page 192

Resize
Selecting Resize allows you to increase or decrease the capacity of the child storage pool, as
shown in Figure 4-39. Enter the new pool capacity and click Resize.
Note: You cannot shrink a child pool below its real capacity. Thus, the new size of a child
pool needs to be larger than the capacity used by its volumes.
Figure 4-39 Resizing child pools
Delete
Deleting a child pool is a task quite similar to deleting a parent pool. As with a parent pool, the
Delete action is disabled if the child pool contains volumes. After deleting a child pool the
extents that were being occupied return to the parent pool as free capacity.
Note: A volume in a child pool can only be migrated to another child pool within the same
parent pool or to its own parent pool. In any other case use volume mirroring instead.
During migration from a child pool to its parent pool, or vice versa, there is no real data
move. There is only a reassignment of extents between the pools.
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Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.1