Storage pools can be defined or updated with a non zero SHRED attribute only if the storage pool CACHE attribute is NO. Existing storage pools with CACHE attribute of YES cannot be updated with a non zero SHRED attribute. Likewise, existing storage pools with a non zero SHRED attribute cannot be updated with CACHE = YES. Existing storage pools with CACHE set to YES cannot be updated with a non zero SHRED attribute. New storage pools cannot be define nor can existing storage pools be modified with CACHE set to YES and a non zero SHRED value.