Choosing a backup system for home or a small business
External drives, NAS devices and cloud backup all have a place. The 3-2-1 rule shows how to combine them.
Published 25 September 2026
The 3-2-1 rule
Keep three copies of your important data, on two different types of storage, with one copy somewhere else. For example: the files on your computer, a backup on an external drive or NAS, and a cloud backup.
External drives
Cheap and simple, and ideal for Time Machine or Windows backups. The downside is that they sit next to your computer, so fire, theft or a ransomware attack can hit both. Rotate two drives and keep one away from the office if you can.
NAS devices
A NAS can back up several computers automatically. A NAS with two or more drives set up as RAID can keep running if one drive fails, but RAID is not a backup: deleted or encrypted files are deleted or encrypted on every drive at once.
Cloud backup
A cloud backup service keeps a copy off-site and often keeps older versions of files, which helps you recover from ransomware or accidental deletion. Check how long versions are kept and how long a full restore would take.
Check it works
Whatever you choose, test a restore regularly. If you would like help setting up backups after a recovery, just ask when you get in touch.