The MDisks that were in the Parent Pool are returned to un-managed mode and can be  added to other Parent Pools. Because the deletion of a Parent Pool can cause a loss of  data, you must force the deletion if volumes are associated with it. Instead of being created directly from MDisks, Child Pools are created from existing capacity  that is allocated to a Parent Pool. As with Parent Pools, volumes can be created that  specifically use the capacity that is allocated to the Child Pool. Child Pools are similar to  Parent Pools with similar properties and can be used for volume copy operation.  Child Pools are created with fully allocated physical capacity. The capacity of the Child Pool  must be smaller than the free capacity that is available to the Parent Pool. The allocated  capacity of the Child Pool is no longer reported as the free space of its Parent Pool. When you create or work with a Child Pool, consider the following general guidelines: GLYPH<SM590000> If the volume is mirrored and the synchronized copies of the volume are all in one pool, the  mirrored volume is destroyed when the storage pool is deleted. If the volume is mirrored  and there is a synchronized copy in another pool, the volume remains after the pool is  deleted. Child Pools GLYPH<SM590000> Child Pools can be created and changed with the command-line interface or through IBM  Spectrum Control when creating VMware vSphere Virtual Volumes. You can use the  management GUI to view Child Pools and their properties. GLYPH<SM590000> As with Parent Pools, you can specify a warning threshold that alerts you when the  capacity of the Child Pool is reaching its upper limit. Use this threshold to ensure that  access is not lost when the capacity of the Child Pool is close to its allocated capacity. GLYPH<SM590000> On systems with encryption enabled, Child Pools can be created to migrate existing  volumes in a non-encrypted pool to encrypted Child Pools. When you create a Child Pool  after encryption is enabled, an encryption key is created for the Child Pool even when the  Parent Pool is not encrypted. You can then use volume mirroring to migrate the volumes  from the non-encrypted Parent Pool to the encrypted Child Pool. GLYPH<SM590000> Ensure that any Child Pools that are associated with a Parent Pool have enough capacity  for the volumes that are in the Child Pool before removing MDisks from a Parent Pool. The  system automatically migrates all extents that are used by volumes to other MDisks in the  Parent Pool to ensure data is not lost.  GLYPH<SM590000> You cannot shrink the capacity of a Child Pool below its real capacity. The system uses  reserved extents from the Parent Pool that use multiple extents. The system also resets  the warning level when the Child Pool is shrunk and issues a warning if the level is  reached when the capacity is shrunk.  GLYPH<SM590000> The system supports migrating a copy of volumes between Child Pools within the same  Parent Pool or migrating a copy of a volume between a Child Pool and its Parent Pool.  Migrations between a source and target Child Pool with different Parent Pools are not  supported. However, you can migrate a copy of the volume from the source Child Pool to  its Parent Pool. The volume copy can then be migrated from the Parent Pool to the Parent  Pool of the target Child Pool. Finally, the volume copy can be migrated from the target  Parent Pool to the target Child Pool GLYPH<SM590000> A Child Pool cannot be created from a Data Reduction Pool. 58  IBM FlashSystem 9200 and 9100 Best Practices and Performance Guidelines