Best backup strategy

The absolute gold standard in data protection is the 3-2-1 backup strategy (nowadays often expanded to the 3-2-1-1-0 rule to also provide protection against ransomware).

The 3-2-1-1-0 Principle

Rule	Meaning	Why?
3	Copies of your data	Keep the original plus at least 2 backups.
2	Different media	Store the backups on two different types of media (e.g., an external SSD/NAS and a cloud server). If one medium fails, you still have the other.
1	Off-site location	Ensure at least 1 copy is located off-site (e.g., in the cloud or on an external drive at a family member's home or office). Protects against fire, theft, or water damage.
1	Offline / Immutable	At least 1 copy is offline or immutable (air-gapped or WORM storage). This prevents ransomware from encrypting your backups along with your PC.
0	Zero errors (Testing)	Regularly perform recovery tests. A backup you cannot restore does not exist.

What does this look like in practice?

For Home Users & Freelancers

1. Original: Files on your laptop/computer.
2. Local Backup: An external SSD or Synology/QNAP NAS that automatically backs up every hour or day (e.g., using Time Machine on Mac or File History / Veeam on Windows).
3. Off-site & Offline Cloud: An automated encrypted cloud backup via services like Backblaze, Proton Drive, or Duplicati to an S3 bucket with immutability (Object Lock).

For Businesses

• Daily Mapping: Local snapshots on an isolated NAS/SAN with strict access controls.
• Automated Off-site Synchronization: Encrypted backups to a secondary data center or cloud provider (e.g., AWS S3, Azure Blob, Wasabi) with overwrite-protection features.
• Tape / Cold Storage: A periodic offline copy that is physically disconnected.

Key Pitfall: Sync services such as OneDrive, Google Drive, or Dropbox are not full backups. If you accidentally delete or corrupt a file, or if ransomware encrypts your files, those changes are immediately synced to the cloud.

(Source: Google Gemini)