The capacity previously used by the LUNs you remove will be initialized and eventually re-used.  The use of standardized 'slices' to allocate capacity within the pool diminishes what is traditionally known as 'fragmentation' when deleting (actually deallocating) capacity from the pool.  The whitepaper EMC VNX Virtual Provisioning: Applied Technologybriefly refers to this reuse of capacity.  That whitepaper is available on Powerlink.
Hi,  I have a CX-480 on Flare30 and have 3 very large storage pools on it.  I need to remove several of the luns on one of the pools and create new ones there.  Do i need to worry about fragmentation in the pools?  I can't find any information on-line about this.  The data moves in prepartion is no issue, is working fine, just wondering if I need to worry about fragmentation.  Thanks, 
Storage Pools - fragment?