| Device | Type | IOPS | Interface | Notes |
| 5,400 rpm SATA drives | HDD | 50-80 IOPS | SATA 3 Gb/s | |
| 7,200 rpm SATA drives | HDD | 75-100 IOPS | SATA 3 Gb/s | |
| 10,000 rpm SATA drives | HDD | 125-150 IOPS | SATA 3 Gb/s | |
| 10,000 rpm SAS drives | HDD | 140 IOPS | SAS | SAS is full duplex |
| 15,000 rpm SAS drives | HDD | 175-210 IOPS | SAS | SAS is full duplex |
In a mirrored configuration:
Disk IOPS = Read IOPS + (2 * Write IOPS)
In a parity (RAID5) configuration:
Disk IOPS = Read IOPS + (4 * Write IOPS)
Example calculations
Now let's look at an example. If you estimate that you need to support 40 Read IOPS (40 reads/sec) and 80 Write IOPS (80 writes/sec).
If you want to use a mirrored configuration of drives:
Disk IOPS = Read IOPS + (2 * Write IOPS) = 40r/s + (2 * 80w/s) = 200 Disk IOPSUsing 7200 rpm drives, you need: 200 / 50 = 4 disk drives
Using 10k rpm drives, you need: 200 / 130 = 2 disk drives (always round up)
If you want to use a parity (RAID5) configuration of drives:
Disk IOPS = Read IOPS + (4 * Write IOPS) = 40r/s + (4 * 80w/s) = 360 Disk IOPSUsing 7200 rpm drives, you need: 360 / 50 = 8 disk drives (always round up)
Using 10k rpm drives, you need: 360 / 130 = 3 disk drives
An excellent article on how how RAID levels effect IOPS
http://skabelka.com/node/125
http://sudrsn.wordpress.com/2010/12/25/iops-raid-penalty-and-workload-characterization/
