Figure 4-38 Resizing child pools Delete 4.3 Working with managed disks Deleting a child pool is a task that is 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 be migrated only 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. A storage pool is created as an empty container, with no storage assigned to it. Storage is  then added in the form of MDisks. An MDisk can be an array from internal storage or an LU  from an external storage system. The same storage pool can include internal and external  MDisks. Arrays are created from internal storage by using RAID technology to provide redundancy  and increased performance. The system supports two types of RAID: traditional RAID and  distributed RAID.  188  Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.2.1