RAID Levels Explained

Every common RAID configuration with capacity formula, fault tolerance, and a detail page when available. Use the calculator for live numbers and the RAID Wizard for a personalised recommendation.

Standard RAID Levels

RAID 0
min 2 drives · 0 fault tol.
Block-level striping with no redundancy. Maximum capacity and speed; single failure = total loss.
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RAID 1
min 2 · survives N−1
Mirror across drives. Simple and reliable for 2-bay setups.
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RAID 5
min 3 · 1 fault tol.
Single distributed parity. Good capacity efficiency for 3-4 small drives. Risky with large drives.
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RAID 6
min 4 · 2 fault tol.
Double parity. Survives 2 simultaneous failures. The default for 5+ drives or 12 TB+ drives.
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RAID 10
min 4 even · 1 per pair
Striped mirrors. Best traditional RAID for IOPS-heavy workloads.
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Vendor-specific

Synology SHR-1
min 2 · 1 fault tol.
Synology Hybrid RAID with single parity. Handles mixed drive sizes natively.
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Synology SHR-2
min 4 · 2 fault tol.
Double-parity SHR. Recommended for larger Synology pools.
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Unraid (1 parity)
min 2 · 1 fault tol.
Independent drives + single parity. Mixed sizes natural, single-drive isolation.
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Unraid (2 parity)
min 3 · 2 fault tol.
Double-parity Unraid. Best for 5+ drive pools or critical data.
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ZFS

RAIDZ1
min 3 · 1 fault tol.
ZFS single parity with checksums and used-block resilver.
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RAIDZ2
min 4 · 2 fault tol.
The ZFS sweet spot. Double parity, checksums, snapshots, replication.
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RAIDZ3
min 5 · 3 fault tol.
Triple parity. Maximum safety for large ZFS pools.
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Other

JBOD
min 1 · 0 fault tol.
Just a Bunch of Disks. No redundancy. Use when data is already safe elsewhere.
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