Storage, made clear
RAID 5 Calculator
Estimate usable storage with single-parity protection. RAID 5 requires at least three drives.
Estimated usable RAID capacity
≈ 21.83 TiB
4 × 8 TB drives in RAID 5
- Raw capacity
- 32 TB
- RAID overhead
- 8 TB
- Storage efficiency
- 75%
- Fault tolerance
- 1 drive
Multiple drive failures may be tolerated if they occur in different mirror pairs.
Estimated RAID-level capacity. Formatting, filesystem metadata and system reservations can reduce the space available for files.
Check your array configuration
Correct the input to see an estimated usable capacity.
Building this RAID array?
You’ll need 4 × 8 TB drives.
Compare RAID levels
| RAID | Usable capacity | Efficiency | Protection |
|---|
Mirror-based protection depends on which drives fail. RAID 10 tolerates at least one drive failure.
Example RAID 5 capacities
| Drives | Raw | Usable | Binary usable |
|---|---|---|---|
| 4 × 8 TB | 32 TB | 24 TB | 21.83 TiB |
| 6 × 8 TB | 48 TB | 40 TB | 36.38 TiB |
| 8 × 8 TB | 64 TB | 56 TB | 50.93 TiB |
How RAID 5 capacity is calculated
At least 3 drives. The equivalent of one drive’s capacity is used for distributed parity. Usable capacity is (N − 1) × drive size, with tolerance for 1 drive failure.
RAID 5 requirements
Use at least 3 equal-capacity drives. RAID 5 tolerates one drive failure; another failure before recovery can cause data loss.
RAID 5 advantages and limitations
RAID 5 balances usable space with single-drive protection. Its parity overhead is equivalent to one drive, so storage efficiency increases as drives are added. Parity updates add write work, and protection is reduced while a failed drive is being replaced and data is recovered.
RAID 5 examples
With four 8 TB drives, RAID 5 provides 24 TB usable from 32 TB raw, with 8 TB of parity overhead. With six 8 TB drives, it provides 40 TB usable from 48 TB raw.
Frequently asked questions
How many drives does RAID 5 require?
Use at least 3 equal-capacity drives. RAID 5 tolerates one drive failure; another failure before recovery can cause data loss.
How is RAID 5 usable capacity calculated?
(Number of drives − 1) × capacity per drive. All drives are assumed to have the same capacity.
How many drive failures can RAID 5 tolerate?
One drive failure. RAID 5 cannot tolerate two simultaneous drive failures.
Does RAID 5 replace a backup?
No. Separate backups are needed for accidental deletion, malware, theft, fire and other risks.
Why does my RAID 5 array show less space in my operating system?
Your operating system may display binary units. Formatting, filesystem metadata and system reservations can also reduce available space.
Choosing a layout? Compare all RAID levels, or try RAID 6, RAID 10.