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. 

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 

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> 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. 

