High Performance MySQL Chapter 6: Server Performance Tuning
When deciding how to configure your disks, consider the possibility of multiple RAID arrays. RAID controllers aren’t that expensive, so you might benefit from using RAID 5 or RAID 10 for your databases and a separate RAID 1 array for your transaction and replication logs. Some multichannel controllers can manage multiple arrays, and some can even bind several channel controllers together into a single controller to support more disks.