Since we are talking about the 'right' things to do for your SAN disks on SQL Server let us not forget to check with you specific SAN manufacturer's best practices/whitepapers as well. Their unique information combined with Microsoft's can create one screaming SAN. LUN sizes, number of disks, SAN stripe or block sizes all contribute to this and usually are specific to the SAN manufacturer. Oh, let us not forget the technical specs on your HBAs as well ... maximum queue depth, read/write buffering and percentage of read/write activity all by drive letter (system DBs, application DB data, application DB log and tempdb) !