Estimate read/write performance for different RAID levels and drive counts.
RAID read performance scales linearly with disk count since reads can be striped across all drives, but write performance is reduced by a RAID-level-specific write penalty. Parity RAID (5, 6) pays a read-modify-write penalty to recalculate and rewrite parity blocks, while mirrored RAID (10) pays a smaller, fixed 2x penalty for writing to both members of each mirror pair. A workload's blended IOPS depends on its read/write mix, since writes consume disproportionately more back-end disk operations.
Read IOPS
read_IOPS = disks × single_disk_IOPS
Write IOPS
write_IOPS = (disks × single_disk_IOPS) / write_penalty
RAID 5 requires 4 back-end I/Os per logical write: read old data, read old parity, write new data, write new parity. RAID 6 requires 6, since it maintains two independent parity blocks: read old data, read both old parities, write new data, write both new parities.
RAID 10 writes are simple duplication — each logical write becomes two physical writes (to the primary and its mirror) with no parity calculation or read-before-write step, making it far more write-efficient than parity RAID at the cost of using half the raw capacity for redundancy.
Yes for a fixed RAID level and workload mix, since both read and write IOPS scale with disk count — but the relative benefit is workload-dependent: read-heavy workloads gain IOPS almost linearly, while write-heavy workloads on parity RAID gain more slowly because each added disk's IOPS is still divided by the same write penalty.