Overview
IOPS are operations per second; throughput is the amount of data transferred. A system can have high IOPS and low throughput with small random blocks, or high throughput and modest IOPS with large sequential blocks.
Engineering considerations
The Storage IOPS Calculator uses a simplified workload model. RAID 5 and RAID 6 parity writes create more backend work than reads, while RAID 1 and RAID 10 commonly require additional mirrored writes. Real performance also depends on cache, controller limits, queue depth, drive latency and workload locality.
How to plan it
Use IOPS when sizing transactional or highly random workloads. Use throughput when sizing large sequential transfers such as media, backup or migration. Always consider latency because an array can have spare bandwidth while still delivering poor application response times.
Design implications
For a practical design, capture read/write mix, average block size, concurrency, peak IOPS and latency requirements. Then compare those requirements with measured vendor performance rather than assuming the headline specification applies to your workload.
Operational considerations
The calculator can help expose the difference between front-end IOPS and backend work, but it is not a storage benchmark.