The Effects of Random IO on Disk Drive Performance

By January 27, 2011Clariion, Storage

I recently had the opportunity to review some performance data from one of our client’s EMC Clariion arrays. I was specifically looking at the read performance of the disk drives during their backup window. I discovered a great visual example showing the effect of random IO on disk drive IOPS and throughput.

The below graph depicts the following metrics:

  • Disk drive seek distance (GB)– green line, scale on the right
  • Disk drive total IO (IOPS) – black line, scale on the left
  • Disk drive total throughput (MB/s) – red area, scale on the right

Zone 1 – Sequential

  • Seek Distance low, less than 1 GB
  • High total IO, 200-275 IOPS
  • High total disk throughput, about 10-13 MB/s

Zone 2 – Getting Random

  • Seek Distance high, 2-6 GB
  • Lower total IO, 25-100 IOPS
  • Lower disk throughput, less than 3-4 MB/s

Zone 3 – Random

  • Seek Distance High, greater than 9 GB
  • Low total IO, less than 25 IOPS
  • Low disk throughput, 1 MB/s