IOPS & Throughput Calculator

A single-page storage sizing calculator. Open index.html in any browser; there is nothing to install or build.

What it does

Module	What it calculates
Workload	Presets (OLTP, VDI, virtual servers, email, file server, analytics, backup, video) that fill in a typical block size and read/write mix
IOPS ↔ Throughput	Solves any one of IOPS, block size or throughput from the other two
Block size table	Throughput and IOPS at block sizes from 512 B to 1 MiB
Array IOPS	Usable IOPS for a RAID 0/1/10/5/6/50/60 array from drive count, IOPS per drive and read/write mix; drives needed for a target IOPS
Capacity	Raw and usable capacity (TB and TiB), efficiency, parity/mirror overhead, hot spares and span groups
Queue depth & latency	Little's law: queue depth = IOPS × latency
System bottleneck	IOPS ceilings for disks, CPU, controllers and network; the lowest one is the system limit

Formulas

• Throughput = IOPS × block size
• Usable array IOPS = drives × IOPS per drive ÷ (read% + write% × RAID write penalty)
• Write penalty: RAID 0 = 1, RAID 1/10 = 2, RAID 5/50 = 4, RAID 6/60 = 6
• Read cache hit ratio = RAM cache ÷ hot working set (capped at 95%); cached reads skip the disks: disk IOPS = drives × IOPS per drive ÷ (read% × (1 − hit) + write% × penalty)
• CPU limit = nodes × CPUs × cores × GHz × % CPU for storage ÷ CPU cycles per I/O
• Controller limit = min(controllers × IOPS each, controllers × GB/s each ÷ block size)
• Network limit = nodes × ports × port bandwidth × usable % ÷ block size
• System IOPS = min(disks, CPU, controllers, network)
• Queue depth = IOPS × latency

Caveats

Drive, CPU-cost and controller figures are typical values, not measurements. The model ignores controller write cache, SSD write amplification and full-stripe writes, and assumes reads are spread evenly over the working set. Use it for planning, then confirm with a benchmark (for example fio) on your own hardware.