I have already posted some best practices regarding SQL Server vs a SAN (some of them apply to non SAN solutions too).
First get to know SQL Server on I/O level by reading the following whitepapers:
Also read the whitepaper Physical Database Storage Design on how to structure you drives and database files.
Test drive your configuration by using the following tools:
- SQLIOSim x86, SQLIOSim x64, SQLIOSim IA64 these are the replacements for SQLIOStress (I found these links here)
While SQLIO is really designed to test your disk subsystem from a performance point of view SQLIOSim is designed to test the robustness of your disk subsystem. SQLIO requires a lot more input on what exactly to test and you can find more information on SQL Server I/O patterns in this presentation by Gert Drapers.
Don't forget to check your waitstats once in a while to see if your SQL Server is waiting for I/O related operations (more info on waitstats can also be found here - in SQL Server 2005 they are well documented in the Books Online).
For SQL Server 2000: DBCC SQLPERF(WAITSTATS)
For SQL Server 2005: SELECT * FROM sys.dm_os_wait_stats