Disk Performance

Calculating IOPS

from: http://www.ufsdump.org/papers/io-tuning.pdf

© 2007 Darren Hoch ­ dhoch@strongmail.com 4Extreme Linux Performance Monitoring Part II

A disk's RD is fixed based on the RPM of the drive. An RD is considered half a revolution around a disk. To calculate RD for a 10K RPM drive, perform the following:

1. Divide 10000 RPM by 60 seconds (10000/60 = 166 RPS)
2. Convert 1 of 166 to decimal (1/166 = 0.0006 seconds per Rotation)
3. Multiply the seconds per rotation by 1000 milliseconds (6 MS per rotation)
4. Divide the total in half (6/2 = 3 MS) or RD
5. Add an average of 3 MS for seek time (3 MS + 3 MS = 6 MS)
6. Add 2 MS for latency (internal transfer) (6 MS + 2 MS = 8MS)
7. Divide 1000 MS by 8MS per IO (1000/8 = 125 IOPS