RAID Calculator - Capacity, Redundancy & Performance

How it works: Data is split into blocks and written across all drives simultaneously. No redundancy—if one drive fails, all data is lost.

Minimum drives: 2 | Usable capacity: 100% | Fault tolerance: None

Best for: Temporary data, caching, or when speed is critical and data loss is acceptable.

How it works: Data is duplicated identically on two or more drives. If one fails, the mirror continues serving data.

Minimum drives: 2 | Usable capacity: 50% | Fault tolerance: All but one drive

Best for: OS drives, databases, and critical data where availability matters more than capacity.

How it works: Combines mirroring with striping, allowing odd numbers of drives. Each block is written to two drives.

Minimum drives: 3 | Usable capacity: 50% | Fault tolerance: Up to half the drives

Best for: Systems needing RAID 1 protection with an odd number of drives.

How it works: Byte-level striping with a dedicated parity drive. Rarely used today.

Minimum drives: 3 | Usable capacity: (n-1) drives | Fault tolerance: 1 drive

How it works: Block-level striping with a dedicated parity drive. Better than RAID 3 for random reads.

Minimum drives: 3 | Usable capacity: (n-1) drives | Fault tolerance: 1 drive

How it works: Block-level striping with distributed parity. Parity rotates across all drives.

Minimum drives: 3 (recommended 4+) | Usable capacity: (n-1) drives | Fault tolerance: 1 drive

Best for: General-purpose storage, file servers, balanced capacity/performance/protection.

How it works: RAID 5 with integrated hot spare distributed across drives for automatic rebuilds.

Minimum drives: 4 | Usable capacity: (n-2) drives | Fault tolerance: 1 drive + auto rebuild

How it works: Block-level striping with double distributed parity. Survives two simultaneous drive failures.

Minimum drives: 4 (recommended 6+) | Usable capacity: (n-2) drives | Fault tolerance: 2 drives

Best for: Large arrays with big drives where URE during rebuild is a concern.

How it works: Striping across mirrored pairs. Combines RAID 1's redundancy with RAID 0's performance.

Minimum drives: 4 (must be even) | Usable capacity: 50% | Fault tolerance: 1 per mirror pair

Best for: Databases, high-transaction applications needing both speed and reliability.

How it works: Striping across multiple RAID 5 groups. Each group can lose one drive.

Minimum drives: 6 (2 groups of 3) | Usable capacity: Total minus 1 per group | Fault tolerance: 1 per group

How it works: Striping across multiple RAID 6 groups. Each group can lose two drives.

Minimum drives: 8 (2 groups of 4) | Usable capacity: Total minus 2 per group | Fault tolerance: 2 per group

How it works: ZFS single-parity RAID with copy-on-write, checksums, and self-healing.

Minimum drives: 3 (recommended 4+) | Usable capacity: (n-1) drives | Fault tolerance: 1 drive

How it works: ZFS double-parity RAID, equivalent to RAID 6. Survives two drive failures.

Minimum drives: 4 (recommended 6+) | Usable capacity: (n-2) drives | Fault tolerance: 2 drives

How it works: ZFS triple-parity RAID. Survives three simultaneous drive failures.

Minimum drives: 5 (recommended 9+) | Usable capacity: (n-3) drives | Fault tolerance: 3 drives

How it works: NetApp's proprietary double-parity RAID, similar to RAID 6.

Minimum drives: 4 | Usable capacity: (n-2) drives | Fault tolerance: 2 drives

How it works: No RAID—drives presented individually or concatenated. No redundancy.

Minimum drives: 1 | Usable capacity: 100% | Fault tolerance: None

Best for: Maximum capacity when data is backed up elsewhere.