e Integrated ContrPoweredge 2950 PERC 5/i, x6 Backplanoller Card raid5

I have an Dell Poweredge 2950 server with x2 3.00ghz cpu’s x4 146GB, SAS, 3.5-inch 15K RPM Hard Drives. 8gb ram I have a PERC 5/i, x6 Backplane Integrated Controller Card this server will be a DB server Windows 2003 std running sql 2005 what stripe size is best for read write performance on raid 5 ? thank you