RAID or backup: understand before buying a NAS
Beginner guide to understand the difference between RAID, backup, external disk, cloud, ransomware, accidental deletion and restoration.
À retenir
Le RAID aide à continuer. La sauvegarde aide à récupérer.
Le RAID protège surtout contre la panne d’un disque. Une sauvegarde protège contre les accidents plus larges : suppression, ransomware, vol, incendie, mauvaise manipulation ou panne complète du NAS.
Comparatif simple
RAID ou sauvegarde : qui protège quoi ?
Les deux sont utiles, mais ils n’ont pas le même rôle. Le piège est de croire qu’un miroir remplace une vraie copie séparée.
Méthode simple
La règle 3-2-1 sans jargon
- 3 copies : les données originales + deux copies.
- 2 supports : NAS + disque externe, autre NAS ou cloud.
- 1 copie hors site : pas dans la même maison si les données sont irremplaçables.
Pour une famille, on peut simplifier : NAS au quotidien, disque externe régulier, et cloud ou copie distante pour les souvenirs les plus importants.
Erreurs fréquentes
Les pièges à éviter
- Dire “j’ai deux disques, donc je suis sauvegardé”.
- Laisser la seule sauvegarde branchée en permanence.
- Ne jamais tester la restauration.
- Oublier la base de données d’Immich ou les volumes Docker.
- Garder toutes les copies au même endroit.
Photos et documents
NAS 2 baies en miroir, disque USB de sauvegarde, et une copie cloud ou externe pour les albums les plus importants.
Photos auto-hébergées
Sauvegarde des fichiers, de la base de données, des volumes Docker et de la configuration. Une restauration testée est indispensable.
Plusieurs services
Prévoir une stratégie documentée : fréquence, destination, rétention, test de restauration et procédure d’urgence.
Un NAS peut être très fiable et pourtant ne pas protéger tes données si la sauvegarde est mal pensée. La vraie sécurité vient de la restauration possible, pas seulement de la présence de plusieurs disques.
#1
The sentence to be retained
RAID mainly helps to keep running if a disk fails. A backup is used to retrieve your data when something more serious happens: accidental deletion, ransomware, theft, fire, configuration error or complete NAS failure.
#2
What RAID protects
RAID protects against certain types of disk failure. For example, in RAID 1, two discs contain the same data. If one disk fails, the NAS can continue to work with the other disk for time to replace the defective disk.
#3
What RAID does not protect
RAID does not protect against accidental suppression. If you delete a photo folder, the deletion is replicated. Nor does it protect against ransomware, theft, fire, overvoltage, mishandling or logical data corruption.
#4
Why RAID sometimes gives a false sense of security
Many beginners think that a NAS with two drives is automatically secure. That's not true. Two mirror discs improve availability, but they do not replace a separate copy. If the entire NAS is lost, both drives can be lost at the same time.
#5
What a real backup is
A backup is a separate copy that allows you to go back. It can be stored on an external USB drive, other NAS, cloud service or other location. The important point is that it does not depend solely on the main NAS.
#6
Rule 3-2-1 simplified
Rule 3-2-1 states: three copies of the data, on two different media, including an off-site copy. For a family, you can simplify: files on the NAS, a backup on external disk, and a remote or cloud copy for the most important memories.
#7
Concrete example: family photos
For family photos, a good base can be: NAS with two mirror discs, regular backup to an external USB drive, and cloud backup or other place for the most valuable albums. The NAS is used daily, the backup is used for accidents.
#8
Concrete example: Immich
With Immich, it's not enough to save the photos folder. You should also think about the database, Docker volumes, configuration files and the restoration procedure. An Immich backup must be tested before being considered reliable.
#9
Why test restoration
Untested backup is a promise, not a certainty. Try to restore some files, an album, or a small part of the data. This test makes it possible to check that the files are legible and that the recovery method is included.
#10
The role of inverter
An inverter does not replace a backup, but it protects the NAS from sudden cuts. It allows the NAS time to shut down cleanly and limits the risk of data corruption. For an important family NAS, it is often underestimated protection.
#11
What level to start with?
To start with, the consistent minimum is a NAS with suitable drives, a simple RAID configuration if needed continuity, and a regular external backup. The upper level adds a remote copy, an inverter and a planned restoration test.
#12
Easy NAS Recommendation
Do not spend the entire budget in the NAS by forgetting the backup. A simpler NAS with a true external copy is often safer than a large NAS without a recovery plan. RAID for continuity, backup for recovery: the two roles are different.