Table 4-13 lists all of the extent sizes that are available in an IBM FlashSystem 9100. This table only shows the maximum extent sizes versus the maximum cluster size when up to  four IBM FlashSystem 9100s are clustered together. For more information on the extents in regular, thin, and compressed pools, and the most  up-to-date information on the IBM FlashSystem 9100 configuration limits, go to the  configuration for the IBM FlashSystem 9100 family. When planning storage pool layout, consider the following aspects: 104  IBM FlashSystem 9100 Architecture, Performance, and Implementation – Put image mode volumes in a dedicated storage pool or pools. – The storage pool goes offline if an MDisk is unavailable, even if the MDisk has no data  on it. Do not put MDisks into a storage pool until they are needed. – An alternative approach is to createa few large storage pools. All MDisks that  constitute each of the pools should have the same performance characteristics. – Using a larger number of smaller pools reduces the failure domain in case one of the  pools goes offline. However, an increased number of storage pools introduces  management overhead, impacts storage space use efficiency, and is subject to the  configuration maximum limit. – The number and size of storage  pools affects system availability.  GLYPH<SM590000> Storage pool reliability, availability, and serviceability (RAS) considerations: – 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. – Pick the extent size and then use that size for all storage pools. – For all of the values and rules for extents, see the previous link.  GLYPH<129> Note that 4 GB is the default now. GLYPH<129> If not using DRP, then 1 GB is acceptable.  GLYPH<129> If using DRP, then it is essential to use 4 GB.  – Generally, use 1 GB or higher: GLYPH<SM590000> Pool extent size: Table 4-13 Extent size and maximum clustered system capacities Extent size Maximum clustered system capacity 0016 MB  064 TB 0032 MB 128 TB 0064 MB 256 TB 0128 MB 512 TB 0256 MB 001 petabyte (PB) 0512 MB 002 PB 1024 MB 004 PB 2048 MB 008 PB 4096 MB 016 PB 8192 MB 032 PB