What this RAID performance calculator estimates
This tool gives a fast, practical estimate of RAID array performance and usable capacity. Enter your drive specs and workload mix, and it returns estimated sequential throughput, random IOPS, capacity efficiency, and write-penalty impact. It is ideal for first-pass planning of NAS, virtualization, backup targets, and media servers.
The model is intentionally simple so you can compare RAID 0, RAID 1, RAID 5, RAID 6, and RAID 10 in seconds. It does not replace vendor benchmarks, but it helps you make better early decisions before buying hardware.
Inputs explained
Hardware inputs
- Number of drives: Total physical disks in the array.
- Capacity per drive: Raw size of each disk (TB) before parity or mirroring overhead.
- Per-drive sequential read/write: Typical MB/s for large contiguous transfers.
- Per-drive random read/write IOPS: Drive-level random performance under realistic queue depth.
Workload inputs
- Read workload %: Ratio of reads versus writes in your application.
- Random block size: Used to convert IOPS to approximate random MB/s.
How the calculator models RAID behavior
The calculator uses commonly accepted RAID approximation rules:
- Usable capacity: Depends on parity or mirroring overhead (for example, RAID 5 loses one drive to parity).
- Sequential read scaling: Usually scales with the number of drives for large reads.
- Sequential write scaling: Reduced for parity RAID levels due to parity updates.
- Random write IOPS: Penalized by RAID write amplification (RAID 5 ~4x, RAID 6 ~6x backend operations).
Write-penalty assumptions used
- RAID 0: penalty 1
- RAID 1: penalty 2
- RAID 5: penalty 4
- RAID 6: penalty 6
- RAID 10: penalty 2
RAID level guidance at a glance
RAID 0
Maximum speed and full capacity usage, but no redundancy. Best for scratch data where loss is acceptable.
RAID 1
Mirroring gives strong protection with simple rebuilds. Great for small critical systems, but capacity efficiency is low.
RAID 5
Good balance between usable capacity and performance for read-heavy workloads. Write-heavy workloads can suffer due to parity overhead.
RAID 6
Similar to RAID 5 but with higher fault tolerance. Better for larger arrays where dual-drive failures are a concern.
RAID 10
Excellent random performance and solid resilience, especially for transactional workloads. Capacity cost is similar to RAID 1.
Important real-world factors this model cannot fully capture
- Controller cache and CPU limits
- Queue depth and mixed block sizes
- Filesystem overhead and fragmentation
- Network bottlenecks (1/10/25/40/100GbE)
- Rebuild state, background scrubs, and thermal throttling
- SSD garbage collection and HDD seek behavior
In practice, treat estimates as planning guidance and validate with benchmarking tools such as fio, vdbench, or vendor utilities.
Example planning workflow
- Start with your target usable capacity and workload mix.
- Compare RAID 5, RAID 6, and RAID 10 with identical drives.
- Check whether write IOPS and mixed throughput meet your SLA.
- Validate redundancy level against business continuity requirements.
- Run real benchmarks before production deployment.
Bottom line
A RAID performance calculator helps you avoid expensive trial-and-error. Use it to quickly compare trade-offs among capacity, speed, and fault tolerance, then confirm the final design with measured testing in your own environment.