Calculating IOPS

IOPS are an important factor when scaling a Virtual Desktop Infrastructure.
There are some good articles about this and ive added links at the bottom of this post.

This simple formula will allow you to determine the IOPS of a physical hard disk.
(1 / (average latency in ms + average seek time in ms).

This figure then needs to be recalculated to match the RAID configuration the disks are running in as the RAID configuration will have an impact on the figure.

Sample drive:

• Model: Western Digital VelociRaptor 2.5″ SATA hard drive
• Rotational speed: 10,000 RPM
• Average latency: 3 ms (0.003 seconds)
• Average seek time: 4.2 (r)/4.7 (w) = 4.45 ms (0.0045 seconds)
• Calculated IOPS for this disk: 1/(0.003 + 0.0045) = about 133 IOPS

RAID Read Penalty is 1 on all RAID configurations
RAID Write Penalty on IOPOS

RAID 0 - 1
RAID 1 - 2
RAID 5 - 4
RAID 6 - 6

Use the following to help calculate the RAID penalty for the real world.
http://www.yellow-bricks.com/2009/12/23/iops/

IOPS Useful links

http://www.brianmadden.com/blogs/rubenspruijt/archive/2010/05/02/vdi-and-storage-deep-impact.aspx

http://blogs.techrepublic.com.com/datacenter/?p=2182

http://virtualfeller.com/