RAID 5 vs RAID 6 — 4×4 TB

You have 4 drives of 4 TB (16 TB raw) and are deciding between RAID 5 (single parity — one drive may fail) and RAID 6 (double parity — two drives may fail). The table shows what each choice actually gives you.

MetricRAID 5RAID 6
Usable capacity12 TB8 TB
Redundancy overhead4 TB8 TB
Storage efficiency75%50%
Fault tolerance (drives)12
Minimum drives34

RAID 5 gives you 4 TB more usable space on this configuration.

RAID 6 survives more simultaneous drive failures — with 4 drives of 4 TB, rebuild windows are long, and that margin is what saves the array when a second drive acts up mid-rebuild.

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