When looking at SQL Server setup it might be worthy of a visit to microsoft for their sql setup, I've previously used 14 disk raid 10 arrays ( 2 ) for data, a 12 disk raid 10 for backups, a 6 disk raid 0 for tempdb and either seperate raid 1 sets for transaction logs or a 6 disk raid 10. Usually placed the log for tempd on a seperate drive. I suppose it's a matter of scale, a single disk can only support a number of i/o's - no matter how you look at it, for high performance oltp systems you need spindles.

My real gripe about the provision of SAN's is the tendancy not to provide dedicated spindles for the sql server, by splitting the spindles the i/o are split and it is very easy to swamp the array and cause big problems for sql server.

I agree a well set up san can perform - well I'm told it can - perhaps we should look at the throughput for backups, this is one of the easiest way to compare a set of disks - how quick does your backup complete ?