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An external drive is the cheapest insurance you can buy for your photos and documents. The choice looks more complicated than it is. For backup, three decisions matter: the type of drive, the size, and the connection. After that, how you use the drive matters more than which one you bought.
Hard drive or SSD?
External drives come in two kinds.
A portable hard drive stores data on spinning disks. It offers a great deal of storage for the money, and it is perfectly good for backup, where speed hardly matters because the work happens in the background. Its weakness is moving parts. A drop while it is running can destroy it.
A portable SSD has no moving parts. It is much faster, smaller, and it survives being dropped, but it costs noticeably more for the same amount of space.
Which should you buy?
- For a backup drive that sits on a desk: a hard drive. Spend the difference on a bigger one.
- For a drive that travels in a laptop bag: an SSD is worth the money.
- For working directly from the drive, editing photos or video: an SSD.
What size?
Find out how much data you have. On Windows, open File Explorer, right-click your user folder and choose Properties. On a Mac, open System Settings, then General, then Storage.
Buy a drive at least twice that size, and more if you can. Backup software keeps older versions of your files, which is the feature that saves you when you overwrite a document or when ransomware scrambles it. Versions need room. For most households that means a 1 TB or 2 TB drive. People with large photo or video collections should look at 4 TB and above.
Which connection?
Almost every current drive uses USB. Two things to check:
- The plug. New computers have the small oval USB-C port. Older ones have the rectangular USB-A port. Many drives include both cables, and an adapter is cheap if yours does not.
- The speed. Anything described as USB 3.0 or newer, which also appears under the names USB 3.1, USB 3.2 and 5Gbps or faster, is fine for backup. Avoid very old or suspiciously cheap drives that are USB 2.0 only.
Portable or desktop?
Portable drives take their power from the USB cable. Desktop drives are larger, need their own power adapter, and offer the largest sizes at the lowest price per terabyte. For a desktop computer that stays in one place, a desktop drive is a sound choice. For a laptop, buy a portable one.
Be careful with bargains
Buy a known brand from a seller you trust. Drives sold with an enormous capacity at an unbelievable price, such as 16 TB for the cost of lunch, are a well-known fraud. They are tiny memory cards altered to report a false size, and they quietly destroy whatever you save once the real space runs out. If a price looks impossible, it is.
Setting it up
Use the backup tool you already have. File History or Windows Backup on Windows, and Time Machine on a Mac. Plug the drive in, choose it as the backup drive, and let it run. Dragging files across by hand is not a backup plan, because it depends on you remembering to do it.
Encrypt it. A backup drive holds a copy of everything, and it is small enough to be lost or stolen. On a Mac, tick the option to encrypt the backup when you set up Time Machine. On Windows, BitLocker To Go can encrypt an external drive on the Pro editions. Keep the password or recovery key in your password manager, not on the drive.
Label it with the date you bought it.
What one drive cannot do
A single external drive on the same desk as the computer protects you from a failed computer. It does not protect you from fire, theft, a power surge, or ransomware that reaches every connected drive.
Two simple ways to close that gap:
- Add an online backup service, so that one copy is always somewhere else.
- Or own two drives and swap them every week or two, keeping the spare at work or with a relative.
How long will it last?
Plan to replace a backup drive every four or five years, and straight away if it starts to click, disconnects by itself, or reports errors. Drives are cheap compared with what they hold. When you replace one, wipe or destroy the old drive, because it still contains a full copy of your files.
For a small office
One USB drive on one PC does not protect a business. Shared files need a backup of wherever they are actually stored, whether that is a server, a network storage box or a cloud service. At least one copy should be kept off the premises, and one named person should check every week that the backups are still running.