Storage Hardware

Storage hardware is the physical path that preserves data and moves it between persistent media and a computer. A complete path includes the storage medium, a device controller, an interface, a host controller or PCI Express connection, firmware, cabling or a backplane, power, and cooling. The operating system normally exposes the result as a block device. File systems, databases, and volume managers build their own structures above that device.

This separation matters because several terms describe different layers. An SSD names a device built from solid-state storage. NVMe names an interface specification optimized for solid-state storage over PCI Express and other transports. M.2 names a form factor and connector family. None of those terms alone states the device's capacity, endurance, latency, or compatibility.

Follow one input/output request

An application asks the operating system to read or write data. The file system or database maps that request to logical blocks. A device driver submits commands through a host interface. The storage controller translates those commands, moves data through a cache or buffer, performs error detection and correction, and addresses the physical medium. A completion travels back through the same layers.

Each layer can change observed behavior. An application may wait for a durable write while a drive still holds data in volatile cache. A cable or backplane can limit link speed even when the device supports a faster interface. A controller can hide individual drives behind one logical unit. A benchmark may therefore measure the whole path rather than the media alone.

Hard disk drives

A hard disk drive, or HDD, stores non-volatile data as magnetic patterns on rotating platters. An actuator positions read and write heads over tracks. Rotation and head movement add mechanical delay, especially for small random requests. Sequential transfers reduce that movement and make better use of the media's sustained transfer rate.