How to Set Up the 3-2-1 Backup Rule in One Afternoon

The 3-2-1 rule is the standard for surviving disk failure, ransomware, theft, and accidental deletion: keep three copies of your data, on two different types of media, with one copy offsite. It sounds heavy, but with a cloud account and an external drive you can build it in an afternoon. This guide walks through the whole setup so nothing important depends on a single device.

What you need

An external USB drive at least as large as the data you want to protect (SSD preferred for speed)
A cloud storage account with enough space: Google Drive (15 GB free), Dropbox (2 GB), Backblaze B2 (pay per GB), or iDrive (10 TB plans are cheap)
Free sync or backup software such as Duplicati, Restic, rclone, or the vendor's own desktop app
A folder inventory: write down which directories hold photos, documents, and work files

Step by step

Choose what to back up. List your top-level folders (Documents, Photos, Projects) and estimate their size. Skip disposable folders like Downloads and app caches.
Create a master folder structure on your computer, for example C:\Data or ~/data, and move everything worth protecting under it. A single root makes every later step trivial.
Copy 1 is your live working set — already done. This is the copy you edit daily.
Copy 2 goes to the external drive. Plug it in weekly and use a mirror tool rather than drag-and-drop: run rclone sync ~/data /media/usb/backup or use FreeFileSync on Windows/macOS. Mirrors update only changed files, so weekly runs take minutes.
Copy 3 goes offsite via cloud. Install Duplicati or restic, point it at your data folder, enable client-side encryption before upload, and schedule nightly backups. Encrypted backups mean the provider cannot read your files.
Verify the first cloud restore immediately. Download two or three random files from the backup target and open them. A backup that has never been restored is a hope, not a backup.
Set calendar reminders: external drive sync weekly, full restore test quarterly.
Document your setup in one page: what tools, where credentials live (a password manager, never a sticky note), and how to restore.

Common mistakes

Keeping the external drive permanently plugged in. Ransomware encrypts connected drives too; disconnect after each sync.
Using two cloud providers but calling that "two media." Both are the same media type — pair cloud with a physical drive instead.
Never testing restores. Corruption discovered during a crisis is too late; test restores quarterly.

Related guides

Cloud backups are only as safe as the encryption protecting them, so read [[encrypt-files-before-upload]] before pushing sensitive data anywhere. Sync tools occasionally produce duplicate "conflicted copy" files that bloat backups — [[prevent-cloud-sync-conflicts]] explains how to avoid them. If you later switch providers, [[migrate-between-cloud-providers]] covers moving your archive without downtime, and [[recover-file-version-history]] shows how version history doubles as a second line of defense against bad edits.