Overview: Storage performance
Storage performance depends on request pattern, queue and service delays, device state and reusable cached data.
A long sequential copy exercises a different pattern from thousands of small file opens. Latency describes the response of an operation, while spin-down and caches change the state it encounters. This group explains those relationships before storage is described with one general speed figure.
Sequential and random I/O
Sequential and random I/O describe the order and size of storage requests, which can affect media reads and library work very differently.Storage latency
Storage latency is the response time of an operation, including waiting in queues as well as the device's own work.Disk spin-down
Disk spin-down stops an idle drive's platters, saving some power while adding a wake interval to a later access.Storage caches
Storage caches retain reusable data or accept writes before slower storage work completes, so cache hits and durable writes have different meanings.