RAID Calculator
Configure Your RAID Array
RAID 5 — 8 × 12 TB
Drive Allocation
This simplified visualization shows the approximate capacity role assigned to each drive. Real RAID controllers distribute data and parity across member drives rather than dedicating specific physical drives permanently to parity.
RAID 5
RAID 5 combines block-level striping with distributed single parity. It requires at least three drives and can tolerate one member-drive failure before the array loses redundancy.
Why RAID Capacity May Look Smaller in Your Operating System
Drive manufacturers normally advertise capacity using decimal units, where 1 TB equals 1,000,000,000,000 bytes. Operating systems and storage tools may display binary tebibytes, where 1 TiB equals 1,099,511,627,776 bytes.
The calculator therefore shows both the manufacturer's approximate decimal capacity and the equivalent binary TiB value. Filesystem formatting, metadata, controller initialization, reserved space and other overhead can reduce final usable filesystem capacity further.
RAID Capacity Formulas
| RAID Level | Minimum Drives | Approximate Usable Capacity | Basic Fault Tolerance |
|---|---|---|---|
| RAID 0 | 2 | N × Drive Size | None |
| RAID 1 | 2 | 1 × Drive Size | Up to N − 1 in a full mirror |
| RAID 5 | 3 | (N − 1) × Drive Size | 1 drive |
| RAID 6 | 4 | (N − 2) × Drive Size | 2 drives |
| RAID 10 | 4 | (N ÷ 2) × Drive Size | Depends on which mirror members fail |
| RAID 50 | 6 | (N − Groups) × Drive Size | 1 drive per RAID 5 group |
| RAID 60 | 8 | (N − 2 × Groups) × Drive Size | 2 drives per RAID 6 group |
RAID Calculator Limitations
This calculator provides planning estimates for arrays using equal-capacity drives. When drives of different capacities are combined, most traditional RAID implementations are constrained by the smallest member drive. Actual usable capacity may also vary by RAID controller, sector size, metadata, filesystem, operating system and vendor-specific implementation.
RAID 10 fault tolerance depends on which mirror members fail. RAID 50 and RAID 60 can survive multiple simultaneous failures only when those failures remain within the tolerance of each individual RAID group.
RAID Is Not a Backup
RAID can improve storage availability and fault tolerance, but it does not create an independent backup of your data. Critical systems should still be protected by an appropriate backup and recovery strategy.
Learn Why RAID Is Not a Backup →