Editing Computer data storage (section)

=== Performance ===
; [[Latency (engineering)|Latency]]: The time it takes to access a particular location in storage. The relevant [[unit of measurement]] is typically [[nanosecond]] for primary storage, [[millisecond]] for secondary storage, and [[second]] for tertiary storage. It may make sense to separate read latency and write latency (especially for non-volatile memory) and in case of sequential access storage, minimum, maximum and average latency.
; [[Hard_ disk drive performance characteristics#Data transfer rate|Throughput]]: The rate at which information can be read from or written to the storage. In computer data storage, throughput is usually expressed in terms of megabytes per second (MB/s), though [[bit rate]] may also be used. As with latency, read rate and write rate may need to be differentiated. Also accessing media sequentially, as opposed to randomly, typically yields maximum throughput.
; Granularity: The size of the largest "chunk" of data that can be efficiently accessed as a single unit, e.g. without introducing additional latency.
;Reliability: The probability of spontaneous bit value change under various conditions, or overall [[failure rate]].
Utilities such as [[hdparm]] and [[sar (Unix)|sar]] can be used to measure IO performance in Linux.