RAID Calculator
The RAID Calculator shows you how much usable storage you actually get from your drives after each RAID level's overhead is applied. Enter your Number of Drives, Drive Capacity, and RAID Level, then click Calculate RAID to see usable capacity, raw capacity, overhead percentage, and fault tolerance — the number of simultaneous drive failures your array can survive without losing data.
RAID Array Setup: Drive Count, Capacity and RAID Level
Usable Storage Capacity, Parity Overhead and Fault Tolerance
Usable Capacity
Raw Capacity
Overhead
Fault Tolerance
RAID 0, 1, 5, 6 and 10 Level Comparison: Capacity, Redundancy and Cost
| RAID Level | Min Drives | Usable Formula | Fault Tolerance | Best For |
|---|---|---|---|---|
| RAID 0 | 1 | N × Drive Size | None | Temp data, scratch space |
| RAID 1 | 2 | N/2 × Drive Size | 1 per pair | OS drives, critical data |
| RAID 5 | 3 | (N-1) × Drive Size | 1 drive | File servers, general use |
| RAID 6 | 4 | (N-2) × Drive Size | 2 drives | Large arrays, archives |
| RAID 10 | 4 | N/2 × Drive Size | 1 per mirror | Databases, high performance |
| RAID 50 | 6 | (N-2) × Drive Size | 1 per group | Large databases, video editing |
| RAID 60 | 8 | (N-4) × Drive Size | 2 per group | Highest reliability requirements |
How RAID Works: Striping, Mirroring and Parity Explained
RAID (Redundant Array of Independent Disks) is a data storage virtualization technology that combines multiple physical drives into a single logical unit. Different RAID levels offer different balances of performance, capacity, and fault tolerance. This calculator helps you determine the usable capacity and overhead for your RAID configuration. See also: estimate data migration time.
When planning storage capacity, understanding RAID overhead is crucial. RAID 0 offers no redundancy but maximum capacity, while RAID 1 mirrors data across drives, using 50% of raw capacity for redundancy. RAID 5 and RAID 6 use parity data distributed across drives, offering a good balance between usable space and protection. Related: Plan your storage capacity.
For enterprise environments, choosing the right RAID level depends on your workload requirements. Database servers often benefit from RAID 10's excellent read/write performance, while archival storage might prioritize capacity with RAID 6. Always consider drive failure rates and rebuild times when selecting your RAID configuration. See also: StorageMath calculators.
Usable Capacity Assumptions and Overhead Caveats
- Actual usable capacity may be lower due to file system overhead and vendor-specific implementations.
- Hot spares reduce available capacity but provide automatic failover protection.
- RAID 5 with large drives (4TB+) has increased rebuild risk. Consider RAID 6 or RAID 10.
- Always verify calculations with your storage vendor's documentation.