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RAID 5 vs RAID 6 — 4×12 TB
You have 4 drives of 12 TB (48 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.
| Metric | RAID 5 | RAID 6 |
|---|---|---|
| Usable capacity | 36 TB | 24 TB |
| Redundancy overhead | 12 TB | 24 TB |
| Storage efficiency | 75% | 50% |
| Fault tolerance (drives) | 1 | 2 |
| Minimum drives | 3 | 4 |
RAID 5 gives you 12 TB more usable space on this configuration.
RAID 6 survives more simultaneous drive failures — with 4 drives of 12 TB, rebuild windows are long, and that margin is what saves the array when a second drive acts up mid-rebuild.
With drives of 8 TB and larger, single-parity rebuilds carry measurable URE risk — check yours in the rebuild calculator.
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Open this exact configuration in the calculator and tweak drives, sizes and levels freely.
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