Migrating data from a large extent pool to a small extent pool

A computer program product for migrating data from a large extent pool to a small extent pool, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, wherein the computer readable storage medium is not a transitory signal per se, the program instructions executable by a processor to cause the processor to perform a method comprising:

• identifying, utilizing the processor, a request to migrate data associated with a volume from a source storage pool having a first rank extent size to a destination storage pool having a second rank extent size smaller than the first rank extent size;
• creating, utilizing the processor, a correspondence between logical volume extents of the volume and physical offset locations within rank extents of the source storage pool;
• and
• migrating, utilizing the processor, data from one or more ranks of the source storage pool to one or more ranks of the destination storage pool, utilizing the correspondence between the logical volume extents of the volume and the physical offset locations within the rank extents of the source storage pool.

A system, comprising:

• a processor;
• and
• logic integrated with the processor, executable by the processor, or integrated with and executable by the processor, the logic being configured to:
• identify a request to migrate data associated with a volume from a source storage pool having a first rank extent size to a destination storage pool having a second rank extent size smaller than the first rank extent size;
• create a correspondence between logical volume extents of the volume and physical offset locations within rank extents of the source storage pool;
• and
• migrate data from one or more ranks of the source storage pool to one or more ranks of the destination storage pool, utilizing the correspondence between the logical volume extents of the volume and the physical offset locations within the rank extents of the source storage pool.