AIX Tip of the Week

Improving I/O Performance with Raid 0+1

Audience: System Administrators

Date: May 7, 2001

If you are experiencing I/O bottlenecks, consider Raid 0+1. I just ran a benchmark where Raid 0+1 reduced the database load time from 30 to 5 minutes. Raid 0+1 is available either in AIX LVM software or in SSA hardware. My preference is Raid 0+1 in SSA hardware because it halves the disk write traffic on the system bus.

If Raid 0+1 is not an option and you have a significant amount of write I/O, try turning off Mirror Write Consistency (MWC). This improved I/O throughput by 60% at one of my accounts. Be aware there is a downside to turning off MWC. You must resynch the disks manually to insure mirror consistency after a system failure.

Bruce Spencer,