The 3-2-1 backup rule.
Three copies of your data. Two different kinds of storage. One copy off-site. That's it — the whole framework in one line.
Three copies of your data
Your working copy counts as one. So do any backups. You want a minimum of three so that a single failure — a dead drive, a corrupted file — doesn't take everything with it.
Example for a home user: the files on your laptop (1), a local Time Machine / File History drive (2), and an online backup like Backblaze (3).
Two different types of storage
Don't keep all your backups on the same kind of media, because the same kind of failure can wipe them out together. Mix things up — an internal SSD, an external hard drive, and a cloud service all count as different types.
This also protects against silent problems like drive firmware bugs that affect an entire product line at once.
One copy off-site
If your house burns down or your office is flooded, local backups go with it. One copy needs to be somewhere physically separate — ideally in another country or region.
Cloud backup is the easy modern answer. For Irish businesses, pick a provider with an EU region so you stay clean under GDPR.
The modern 3-2-1-1-0 variant
Some backup specialists extend the rule: 3 copies, 2 media types, 1 off-site, 1 offline/immutable, 0 errors after testing. The two additions matter because of ransomware and silent corruption.
- Immutable / offline: a copy that can't be encrypted or deleted by an attacker who gets into your systems.
- Zero errors: actually test your restores. A backup you've never restored from isn't a backup — it's a hope.
Ready to set up your first off-site copy?
For most homes and small businesses, Backblaze or Acronis handle the off-site part for you automatically.