Should I buy an SSD or a hard drive for backups?

Which drive type suits which job, why the answer for backups differs from the answer for everyday use, and what actually determines how long a drive survives.

Difficulty: beginner
Time: 15 min
Read: 3 min

Short answer

For a backup drive that sits in a drawer, a mechanical hard drive is usually the better buy: far more capacity per pound, and slow speed does not matter for an overnight backup. For a drive carried around in a bag, an SSD is better because it has no moving parts to damage.

The two are not competing for the same job. Speed matters when you are working from a drive; capacity and durability matter when you are storing a copy of everything.

The 3-2-1 backup rule

Step by step

Decide which job the drive is for.A stationary backup at home, a portable drive carried daily, or a working drive you edit files on. These three point at different answers.
Choose a hard drive for bulk backup at home.You get several times the capacity for the same money. A backup runs unattended, so the slower speed costs you nothing.
Choose an SSD for anything that moves.No moving parts means it survives being knocked, dropped in a bag, or carried in a coat pocket. A mechanical drive is genuinely fragile while spinning.
Buy at least twice the size of what you are backing up.Versioned backups accumulate. Both Windows File History and Time Machine keep older versions until the drive fills, and more headroom means more history.
Ignore the interface speed for backup use.A mechanical drive cannot saturate even an older connection, so paying for the fastest interface on a backup drive achieves nothing.
Understand that neither type is archival.Hard drives fail mechanically, and SSDs can lose data if left unpowered for years. Neither is a place to leave the only copy of something for a decade.
Plan for two, not one.The rule that works is three copies, on two kinds of storage, with one off site. A single external drive next to the computer fails all three tests.
Check the drive occasionally.Plug it in, confirm the backup ran, and restore one file. A drive that has quietly stopped being written to is the commonest backup failure.

Tips

For a drive that never leaves the house, a desktop hard drive with its own power supply is cheaper per terabyte than a portable one.
Enable encryption on any backup drive. It contains a complete copy of everything and is small enough to be stolen.
Buy from a retailer with a real returns process. Suspiciously cheap high-capacity drives from marketplace sellers are a known category of fake.

Common mistakes

Keeping the backup drive permanently plugged in — Ransomware, a bad deletion and a power surge all reach an attached drive. Disconnecting between backups is the cheapest protection there is.
Treating one external drive as the backup — It sits in the same house as the computer, so it does not survive fire, flood or burglary — and drives fail. It is one copy, not a strategy.

If it doesn't work

Backup drive is full

Cause: Versioned backups filling the available space — Fix: Both major backup tools prune old versions automatically when full. A larger drive simply buys more history; nothing is broken.

Drive clicks or is not recognised

Cause: Mechanical failure, or a failing cable — Fix: Try a different cable and port first. If it clicks, stop using it — repeated attempts make professional recovery harder and more expensive.

Drive works on one computer but not another

Cause: The format is specific to one operating system — Fix: Use exFAT for a drive that must work with both Windows and macOS, accepting that it lacks the safeguards of the native formats.

Questions people ask

How long does an external drive last?

There is no reliable number. Some fail in a year and some run for a decade. That unpredictability is exactly why the rule is multiple copies rather than one good drive.

Is a network drive better than an external one?

For a household with several computers, often yes — it backs up everything without plugging anything in. It is still one copy in one building, so an off-site copy is still needed.