RAID 10 Capacity Calculator
Calculate usable capacity of a RAID 10 striped-mirror array from disk count and size.
About RAID 10 Capacity Calculator
RAID 10 combines mirroring (RAID 1) and striping (RAID 0) by creating mirrored pairs of disks, then striping data across those pairs. Usable capacity is exactly half the raw capacity. It offers both good random I/O performance (from striping) and redundancy (from mirroring), tolerating one disk failure per mirror pair without data loss.
Formula
RAID 10 usable capacity
usable = (n / 2) × disk_size
- n
- total disk count (even)
- S
- capacity per disk
Worked example
With the default values below, RAID 10 Capacity Calculator returns Usable Capacity of 4,000.00. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Number of Disks (must be even)minimum 4
- 4
- Size per Diskminimum 0.001 GB
- 2,000 GB
Results
- Usable Capacity
- 4,000.00 GB
- Raw Capacity
- 8,000.00 GB
- Mirror Overhead
- 4,000.00 GB
- Storage Efficiency
- 50.00%
- Fault Tolerance
- Tolerates 1 failure per mirror pair
Step by step
- 1Disk count (n, even)= 4
- 2Disk size= 2000 GB
- 3RAID 10 usable capacity= 4000 GB
- 4Mirror pairs= 2 pairs
- 5Storage efficiency= 50%
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why does RAID 10 require an even number of disks?
RAID 10 mirrors disks in pairs before striping across pairs, so each disk needs a partner — an odd number leaves one disk without a mirror, which most controllers do not allow.
Is RAID 10 faster than RAID 5?
For random writes, yes — RAID 10 has no parity calculation overhead, so write latency is lower. Read performance is comparable or slightly better due to mirror read splitting.