I am reconfiguring the storage in our CX600 and was wondering if I should be setting up some of the RAID Groups as RAID 3 instead of RAID5 as they were previously. We have 3 types of servers that use the SAN storage, SQL, Exchange, VMWare ESX. I know that RAID 5 imposes a large penalty for write operations and thought that maybe RAID 3 would be a better choice, but I am not sure if that is the case with applications like SQL and Exchange that have a lot of small I/O (or VMFS volumes for that matter).

The SQL servers are core to our business and do HEAVY processing 24x7 so any improvement in performance helps greatly.

The Exchange servers are fairly light and I am not overly concerned about running them on RAID 5 unless RAID 3 is just a no-brainer (they currenlty run on RAID 5 local disks and soon will be clustered).

VMware is used for everything else, general purpose servers, web servers, domain controllers, application servers, etc. Again, not as concerned about them but I am not sure how VMFS or the general I/O pattern of VMWare would perform on RAID 3.

My question is, should I use RAID 3 for any of these? Pros/Cons?

I realize that the best solution to any of these would be RAID 1/0 but at this time I cannot afford the cost of losing half of my storage space, although I will be pushing it for next years budget!

Thanks for any input and assistance.