IOPS & RAID Write Penalty Calculator
Raw drive IOPS and the IOPS your application actually sees are very different numbers once RAID overhead and read/write mix are accounted for — this is the standard storage-vendor sizing formula, not a rule of thumb.
Raw disk IOPS
Write penalty applied
Effective (host-facing) IOPS
Every write to a parity or mirrored array costs more than one physical
I/O — RAID 5 reads old data and parity, then writes new data and
parity (4 operations per logical write); RAID 6's double parity costs
6. This is why write-heavy database workloads often perform worse on
RAID 5/6 than the raw drive specs suggest.
Raw IOPS needed (after penalty)
Drives required