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RAIDZ1 vs RAIDZ2 — 6×8 TB
You have 6 drives of 8 TB (48 TB raw) and are deciding between RAIDZ1 (ZFS single parity with checksums) and RAIDZ2 (ZFS double parity with checksums). The table shows what each choice actually gives you.
| Metric | RAIDZ1 | RAIDZ2 |
|---|---|---|
| Usable capacity | 40 TB | 32 TB |
| Redundancy overhead | 8 TB | 16 TB |
| Storage efficiency | 83% | 67% |
| Fault tolerance (drives) | 1 | 2 |
| Minimum drives | 3 | 4 |
RAIDZ1 gives you 8 TB more usable space on this configuration.
RAIDZ2 survives more simultaneous drive failures — with 6 drives of 8 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.
See it live
Open this exact configuration in the calculator and tweak drives, sizes and levels freely.
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