What Is an SSD?

An SSD, or solid-state drive, is a storage drive that holds data on flash memory chips rather than on spinning disks. “Solid state” is the electronics term for a circuit with no moving parts, which is the defining feature of the drive. It does the same job as a hard drive: it keeps the operating system, applications and files when the power is off.

So when people search for the SSD meaning, the short answer is non-volatile storage built from chips. Because nothing has to spin up or move a read head, an SSD finds any piece of data in a fraction of a millisecond, which is why a computer with one boots and opens programs so much faster. SSDs have replaced hard drives as the main drive in almost every new laptop, desktop and industrial computer.

Every SSD has three main parts: NAND flash chips that hold the data, a controller that manages them, and usually a DRAM cache that holds the drive’s map of where everything is stored. Some low-cost NVMe drives skip the DRAM and borrow a little of the host’s memory instead.

Flash memory has two awkward habits that the controller hides from the computer. It cannot overwrite data in place, and each cell wears out after a set number of program/erase cycles. The controller’s firmware handles both with a few standard techniques.

The interface sets an SSD’s speed ceiling, and the form factor sets where it fits. A SATA SSD uses the same link as a hard drive, while an NVMe SSD talks to the processor directly over PCIe lanes. The figures below are typical sequential read speeds for current drives.

Real systems rarely reach the headline figure for long. Random access, file size, heat and the drive’s cache all pull it down, so the right interface depends on the workload rather than on the biggest number.

A hard drive stores data magnetically on platters spinning at 5,400 to 7,200 rpm and reads it with a head on a moving arm. Each random read waits for the arm to move and the platter to turn, typically around 10 ms. An SSD answers in roughly 0.1 ms. Hard drives still cost less per terabyte and remain common for bulk archives and video retention, but SSDs win on speed, power, noise and tolerance of movement.

A consumer SSD is designed for a desk: room temperature, a few gigabytes written a day and a product refresh every year or so. An industrial SSD is designed for a cabinet, a vehicle or a machine that has to run for years, and the datasheet says so.

With no fan and no moving parts, an SSD is the natural partner for fanless PCs, which are sealed against dust and often mounted where vibration would shorten a hard drive’s life. Smaller embedded boards often carry eMMC soldered to the board for the operating system, with an M.2 slot for a larger SSD.

Vehicles add shock, vibration and sudden power loss at ignition-off. Many of our in-vehicle computers take removable or hot-swap SSD trays, so recorded data can be taken off the vehicle at the depot without opening the computer.

We fit the right SSD to every system we supply as standard, choosing the interface, flash type, endurance and temperature rating for the workload, then image and validate the system before it ships.