RAID Is Not a Backup – Why You Still Need a Backup Strategy
This is probably the most important thing to understand about RAID: it protects against drive failure, not against data loss. These are fundamentally different problems, and confusing them can cost you everything.
What RAID Protects Against
RAID with redundancy (1, 5, 6, 10, SHR, Unraid, RAIDZ) handles exactly one scenario: a hard drive dies, and you keep running. The array rebuilds onto a replacement drive, and no data is lost. This is about uptime and hardware resilience.
What RAID Does NOT Protect Against
RAID cannot help you with accidental deletion (you delete a file, RAID faithfully deletes it across all drives), ransomware (encrypts your files, RAID faithfully stores the encrypted versions), software bugs (a corrupted database update propagates to all copies), controller failure (a bad RAID controller can corrupt the entire array), fire, theft, or flooding (all drives are in the same box), firmware bugs (a drive firmware issue can corrupt data silently), or human error (reformatting the wrong volume).
In every one of these scenarios, RAID does exactly what it's supposed to – it keeps all drives in sync. The problem is that "in sync" means "all equally corrupted."
The 3-2-1 Backup Rule
The industry standard minimum is: 3 copies of your data, on 2 different types of media, with 1 copy offsite. Your NAS RAID counts as copy number one. A backup drive or second NAS is copy two. A cloud backup (Backblaze B2, Wasabi, etc.) or a drive at a friend's house is copy three.
Practical Backup Strategy for Homelabs
Tier 1 (critical): Family photos, documents, financial records → RAID NAS + external drive rotation + cloud backup (encrypted). Tier 2 (replaceable but annoying): Media library, game ISOs, Linux ISOs → RAID NAS + occasional external backup. Tier 3 (easily replaceable): Downloads, temp files, caches → RAID NAS only, or no backup.
Not all data is equal. Spending $20/month on cloud backup for 40TB of Linux ISOs makes no sense. But your family photos? Those are irreplaceable.
Try it yourself! Compare RAID configurations with your drive sizes.
Open RAID Calculator →RAID + Backup = Sleep Well
Think of RAID as your first line of defense – it keeps you running when hardware fails. Backups are your safety net when everything else fails. You need both. Use our calculator to plan your RAID configuration, then add a backup strategy on top.
Further reading
RAID 0 Explained: Speed Without a Safety Net
RAID 5 vs RAID 6: Which Should You Actually Pick?