hardware//storage//cache

A storage cache is a fast buffer (usually DRAM or SLC flash) between the host and the storage medium. Its layers include the OS page cache, the drive's internal DRAM and ZFS's ARC.

A storage cache is a fast buffer (usually DRAM or SLC flash) between the host and the storage medium. Its layers include the OS page cache, the drive's internal DRAM and ZFS's ARC.

Write-back caches acknowledge writes before they reach the platter or the NAND, which boosts throughput at the cost of a window of risk if power is lost.

Read caches keep hot blocks in memory to avoid the latency of a mechanical seek or a flash read.

It is the same principle as the CPU cache (nanoseconds) and the network cache (milliseconds), applied at the microsecond scale.