Storage, made clear
RAID 10 Calculator
Estimate usable storage across mirrored pairs. RAID 10 requires at least four drives and an even drive count.
Estimated usable RAID capacity
≈ 14.55 TiB
4 × 8 TB drives in RAID 10
- Raw capacity
- 32 TB
- RAID overhead
- 16 TB
- Storage efficiency
- 50%
- Fault tolerance
- At least 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 10 capacities
| Drives | Raw | Usable | Binary usable |
|---|---|---|---|
| 4 × 8 TB | 32 TB | 16 TB | 14.55 TiB |
| 6 × 8 TB | 48 TB | 24 TB | 21.83 TiB |
| 8 × 8 TB | 64 TB | 32 TB | 29.10 TiB |
How RAID 10 capacity is calculated
At least 4 drives and an even number of drives. Half of the raw capacity is usable. At least 1 drive failure is tolerated. Multiple drive failures may be tolerated if they occur in different mirror pairs.
RAID 10 requirements
Use at least 4 equal-capacity drives, with an even number of drives. The drives form mirrored pairs, and data is striped across those pairs. Fault tolerance is at least 1 drive. Multiple failures can sometimes be tolerated if they occur in different mirror pairs and at least one drive in every pair remains intact. Losing both drives in any one mirror pair can cause data loss.
RAID 10 advantages and limitations
RAID 10 combines mirroring and striping. It avoids parity calculations and can suit workloads with frequent writes, though actual performance depends on the hardware and workload. Half of the raw capacity is used for mirrored copies, and protection against multiple failures depends on which drives fail.
RAID 10 examples
Four 8 TB drives form two mirrored pairs, providing 16 TB usable from 32 TB raw. Eight 8 TB drives form four pairs, providing 32 TB usable. In a four-drive array, two failures in different pairs may be tolerated; two failures in the same pair are not.
Frequently asked questions
How many drives does RAID 10 require?
Use at least 4 equal-capacity drives, with an even number of drives. The drives form mirrored pairs, and data is striped across those pairs. Fault tolerance is at least 1 drive. Multiple failures can sometimes be tolerated if they occur in different mirror pairs and at least one drive in every pair remains intact. Losing both drives in any one mirror pair can cause data loss.
How is RAID 10 usable capacity calculated?
(Number of drives ÷ 2) × capacity per drive. All drives are assumed to have the same capacity.
How many drive failures can RAID 10 tolerate?
At least one drive failure. Multiple failures may be tolerated across different mirror pairs, provided no pair loses both drives.
Does RAID 10 replace a backup?
No. Separate backups are needed for accidental deletion, malware, theft, fire and other risks.
Why does my RAID 10 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 5, RAID 6.