Stands for "Input/Output Operations Per Second." IOPS is a metric used to measure to performance of a storage device or storage network. The IOPS value indicates how many different input or output operations a device or group of devices can perform in one second. It may be used along with other metrics, such as latency and throughput, to measure overall performance.
An IOPS value is typically synonymous with "total IOPS," which includes a mix of read and write operations. However, it is also possible to measure more specific values, such as sequential read IOPS, sequential write IOPS, random read IOPS, and random write IOPS. Higher values mean a device is capable of handling more operations per second. For example, a high sequential write IOPS value would be helpful when copying a large number of files from another drive.
SSDs have significantly higher IOPS valued than HDDs. Since SSDs do not have a physical drive head that moves around the drive, they can perform over 1,000 times more read/write operations per second than a typical hard drive. For example, a hard drive that spins at 7200 RPM may have a total IOPS value of 90. A modern SSD may have an IOPS value above 100,000. Some high-end flash drives have IOPS measurements above one million.
While IOPS was important when measuring hard drive performance, most real-world situations do not require more than a thousand inputs/outputs per second. Therefore, IOPS is rarely viewed as an important metric in SSD performance. Latency and throughput are the primary factors that affect SSD speed, while storage capacity and durability (lifespan) are also important to consider.