Exactly right.  I thought my post was reasonably clear on both those counts, but so everyones clear i'll adjust it to:   We do see that for most application workloads, an individual LUN performs significantly better as a thin (VP) compared to thick because a single TDEV can be bound to a pool with many disks compared with a single thick lun that can only address 2/4/8/16 disks depending on the RAID type.  Where multiple thick LUN's perform better than thin LUN's is with sequential write workloads directed at Raid 5 7+1 or Raid 6 configurations.  This is because with thick LUN's, the symm can use Optimised writes (single write for parity and all data for a given raid stripe from cache) whereas with Virtual Provisioning having a 768KB stripe size, a sequential workload directed to the TDEV will most likely not result in optimised writes to the backend and we see a significant increase in backend I/O's to destage data.  This is due to the fact that the raid stripe and the VP stripe are not size aligned so we are unlikely to get all the data elements for the raid stripe to calculate parity.  Raid 1 and Raid 5 3+1 do not have this issue as we dont use parity for raid 1, and the VP and raid stripe sizes are the same for Raid 5 3+1 (Being 768KB).
Hi,  Is it EMC's recommendation not to use FAT devices at all if it can be helped? I know there are a couple of very specific areas where Thin provisioned device is not supported yet e.g SRDF/EDP R21 devices. In a normal scenario is there any peformance benefit in having a Thick/FAT device mapped to a host over a thin. I understand the VMAXe (the baby brother of VMAX) will be fully thin provisioned. I wonder will it be a case that the move will be to only have thin devices mapped to an FA and thick devices are the back end implementation for pool provisioning. Very general query I know but was just wondering is there any performance benefit to thick devices over thin. BTW in our 2 x VMAX (with SRDF/S)  we have implemented thin full provisioned devices as recommended by EMC SA.  Thanks, Victor
Thick Provisioning yesterday's news?