The 3-2-1 Rule

How to complete The 3-2-1 Rule

The 3-2-1 rule is the baseline backup standard that survives the three things that actually destroy data: drive failure, theft or fire, and accidental deletion or ransomware. By keeping copies on two device types plus one location you don't physically control, no single event can wipe you out.

1. Inventory what's truly irreplaceable first (photos, documents, tax records, projects) and skip anything you could re-download.
2. Keep the working copy on your computer as copy one.
3. Buy an external drive at least twice your data size and clone to it on a schedule as copy two.
4. Sign up for a cloud backup like Backblaze or iDrive, or sync the folder to Google Drive, as the offsite copy three.
5. Automate the external backup with Time Machine or File History so it isn't a chore you forget.
6. Pull one file back from each copy to confirm the backups actually restore.

Tips

• Two copies on the same drive don't count; the two-media rule means physically separate devices.
• Encrypt the cloud and external copies if they hold sensitive documents.
• A sync service alone is not a backup; deleting or corrupting a file syncs that loss everywhere.

What counts as done

You can name where all three copies live and successfully restore a test file from both the external drive and the cloud.