IOPS

Input / Output Operations Per Second, IOPS, is a computer benchmark computer storage media. It specifies how many input and output commands per second can be carried out. This information can not be specified in more detail:

• Total IOPS Average number of output operations per second
• Read IOPS Average number of outputs per second
• Write IOPS Average number of inputs per second

The higher the IOPS value, the faster the disk. New storage media such as an SSD can reach up to 10,000 IOPS. SSDs with SandForce 2281 controller, up to 85,000 IOPS reach (as of May 2011). The performance of conventional disks is dependent on the rotational speed and the associated electronics. S- ATA II hard drives with 7200 min-1 and an average access time of 5-6 ms reach about 120 IOPS, while FC disks can reach about 340 IOPS 15k min -1.

While hard drives deliver performance that upstream RAID controller limit this power. An Enterprise Virtual Array system achieved 210,000 IOPS ( EVA8100 ). To achieve this performance it is necessary permanently constructed at least 620 disks. If higher values ​​than the sum of all hard drives achieved, so this is only about the use of the caches, the main memory of the storage system ( In the Unix and Windows caching usually takes place in the servers, whereby low cache hit Council be achieved in the storage system ).

Criticism

The measured IOPS values ​​depend on the access pattern (sequential / random) as well as from cache and / or I / O scheduler settings for the hard drive controller or the operating system, so can usually more than 120 IOPS at S -ATA II disks (see above ) are measured. In particular manufacturer values ​​are therefore not comparable with each other; a statement on its own practicalities can not be seen from the paper data. Also undefined is the value 1 IOPS, making comparisons of values ​​in MB / s impossible. The measure IOPS thus lacks any scientific and is meaningful only as a relative measure in a defined environment.

The value can be used, however, so that makes sense within a data center, to find, for example, the best disk configuration of a server. It also helps if application manufacturers also supply an application- related testing, as practiced by Oracle for its database, version 11.1.