Simple definition
Storage latency is the time required to complete an input/output operation, typically measured in milliseconds or microseconds.
Purpose and use
Storage latency measures how long an operation takes at a specified observation layer.
How does it work?
It may include queueing, processing and transport, so application, host and array measurements can differ.
Example and verification
Review percentiles and spikes alongside load, I/O size and queue depth.
Points to watch
A low average can hide serious delays. One metric alone cannot automatically attribute the cause to a disk.
In short
A useful measurement identifies viewpoint, interval and workload characteristics.