STORAGE SUBSYSTEMS DON'T GET nearly enough attention, though they're arguably the most important subsystem of a modern PC. Of course, they store all of a system's data—an increasingly precious resource that most of us don't back up nearly often enough. Storage subsystems are often the slowest components in a modern PC, as well. Hard drives are essentially mechanical devices, and even with ever-growing platter densities, their seek times can amount to a practical eternity in computer time. Modern storage subsystems have a trick up their sleeves, though. RAID arrays have the potential to improve storage performance dramatically by spreading data over multiple drives. They can also improve redundancy, allowing a system to survive one or more drive failures with no data loss.Read on over here.
Chipset SATA and RAID performance compared

The Tech Report has compared the performance of Serial ATA and RAID.