One of the basic storage pool parameters is the extent size. All MDisks in the storage pool  have the same extent size, and all volumes that are allocated from the storage pool inherit its  extent size.  There are two implications of a storage pool extent size: The SAN Volume Controller supports extent sizes 16 mebibytes (MiB) - 8192 MiB. The extent  size is a property of the storage pool and is set when the storage pool is created.  The extent size of a storage pool cannot be changed. If you need to change extent size, the  storage pool must be deleted and a new storage pool configured.  Table 3-2 lists all of the available extent sizes in a SAN Volume Controller, and the maximum  managed storage capacity for each extent size. When planning storage pool layout, consider the following aspects:  74  Implementing the IBM System Storage SAN Volume Controller with IBM Spectrum Virtualize V8.2.1 GLYPH<SM590000> Pool extent size: – Generally, use 128 MiB or 256 MiB. The IBM Storage Performance Council (SPC)  benchmarks use a 256 MiB extent.  – Pick the extent size and then use that size for all storage pools. – You cannot migrate volumes between storage pools with different extent sizes.  However, you can use volume mirroring to create copies between storage pools with  different extent sizes. GLYPH<SM590000> Maximum volume, MDisk, and managed storage capacity depend on extent size (see  http://www.ibm.com/support/docview.wss?uid=ibm10744461 ). The bigger the extent  defined for the specific pool, the larger is the maximum size of this pool, the maximum  MDisk size in the pool, and the maximum size of a volume created in the pool. GLYPH<SM590000> Volume sizes must be a multiple of the extent size of the pool in which the volume is  defined. Therefore, the smaller the extend size, the better control over volume size. Table 3-2 Extent size and total storage capacities per system Extent size (MiB) Total storage capacity manageable per system 0016  64 tebibytes (TiB) 0032 128 TiB 0064 256 TiB 0128 512 TiB 0256  1 pebibyte (PiB) 0512 2 PiB 1024 4 PiB 2048 8 PiB 4096 16 PiB 8192 32 PiB