Input/output operations per second (IOPS) is a computer performance measure standard. A IOPS number reflects the number of read and write operations that can be performed with both sequential and random data (random data would be files not saved contiguously -- as a drive has more data saved to it over time, its free space becomes fragmented and data is less likely to be saved contiguously).
An average SATA 7,200 rpm hard disk drive should run at about 100 IOPS. (Serial AT Attachment is the interface that connects the drive to a computer. Most storage drives in use today are SATA drives. See the Tip of the Night for January 22, 2016. )
The number of IOPS generated by a RAID (Redundant Array of Independent Disks) is a key consideration in cloud computing. You can help evaluate the strength of cloud data storage with the RAID Calculator.
The RAID Calculator lets you select between SSD (Solid State Drives) and SAS (SCSI) hard drives, and choose the number of disks in the array, the overall hard drive capacity, and the percentage of data that is either being read or wrote.
The calculator gives IOPS numbers for different RAID levels - RAID 5 (these, which require at least 3 disks, are susceptible to failure and not recommended); RAID 6 (which can handle the failure of two different drives, and requires at least 4 drives); and RAID 1+0 (which has a series of mirrored drives and can function even if multiple drives are lost, and also requires at least 4 drives). RAID 1+0 has better read and write performance than both RAID 5 and RAID 6. RAID 1+0 will typically be used for databases. RAID 6 for web servers, or other servers which must store a lot of data. RAID 5 is used for data archiving and warehousing.
For a RAID with 24 200 GB SSD drives tested reading and writing data in equal percentages, a RAID 5 level configuration will function at 96,000 IOPS and a RAID 6 at about 68,000 IOPS. With the RAID 1+0 configuration the IOPS rises to 160,000.