Practical guide

RAID is not backup: what each one protects

A NAS configured with RAID 1 can keep a home archive available after one disk fails, provided the remaining disk and the NAS still work. RAID 0 offers no protection against a disk failure. A backup provides a separate, recoverable copy for deleted, overwritten, encrypted or otherwise damaged files.

Published September 13, 2026 · CDRinfo editorial desk

What RAID does well

In a redundant array, information is spread across drives in a way that can tolerate a specified disk failure. Depending on the configuration, the NAS can continue operating while you replace a failed drive. That can avoid downtime and reduce the pressure to make rushed recovery decisions. It is especially useful when several people depend on the same shared files.

RAID can also provide a larger logical volume or improved read performance. Those are convenience and availability benefits. Keep a second independent record of the files in a backup.

Risks shared by the array

If a file is deleted, encrypted by malware, overwritten by an application, or damaged before the NAS notices, the changed data can be reflected across the whole array. A RAID controller fault, power incident, NAS software failure, theft, fire, or an incorrectly configured rebuild can affect every drive together.

Snapshots can retain earlier versions on the same NAS. Use snapshots for earlier versions and keep a separate backup elsewhere.

Build the two layers deliberately

Use RAID when continuous access matters and the budget allows it. Then back up the NAS to storage outside the array. A direct USB backup can handle a device failure; an encrypted cloud destination or another location can handle an incident at home. Keep more than one backup version so last month’s healthy version remains available after today’s problem becomes visible.

A simple household setup might be a two-bay NAS with redundancy, a scheduled copy to an external drive, and a selected off-site copy of irreplaceable photographs and documents. Choose the files that would be difficult to recreate and add the remaining large video files as capacity allows.

Know the recovery question

Ask a concrete question: “If this folder disappeared on Tuesday, where would I recover Monday’s version?” A recovery answer should name a separate device, destination, date, and recovery method.

Test that answer. Restore a folder to a different location, open several files, and confirm that permissions and file names make sense. Record the recovery time so the household knows what to expect during an emergency.

Choose for the risks you need to cover

Use RAID for resilience and convenience. Budget separately for backups and restore testing so the family archive has a recoverable copy.

Further reading: CISA ransomware guidance and Synology on reducing data-loss risk.