SQL is one of the most I/O intensive business critical applications and especially here it is really important that you have a look at the best practices.
More Details about Performance, Disk Alignment, Storage Recommendations, I/O improvements ….. can be found at at :
Jimmy May his Blog (SQL CAT Member)
Troubleshooting SQL 2005 Performance
SQL CAT (Customer Advisory Team)
Database Mirroring Best Practices in regards to Performance
Storage Top 10 – Best Practices