RAID Capacity Estimator
Estimate raw capacity, usable capacity, parity or mirror overhead, and resilience trade-offs across common RAID layouts.
Input
Estimate usable RAID capacity across common layouts without pretending raw disk total is the same thing as planning truth.
Result
Usable capacity, overhead, and resilience notes for the selected RAID layout.
What this means
This RAID 6 layout reserves the equivalent of two active disks for parity and leaves 1 disk as hot spare. It favors resilience over usable capacity.
The usable result is based on RAID 6 capacity behavior, active disks after spare reservation, and a decimal display base.
Use this for planning-level RAID capacity checks before moving into filesystem overhead, vendor reserve assumptions, or deeper storage design decisions.
Common presets
RAID planning quick guide
Raw capacity is not usable capacity, and pretending otherwise is how people walk into bad storage assumptions.
Parity overhead
RAID 5 and RAID 6 reserve effective disk capacity for parity protection, reducing usable space in exchange for resilience.
Mirror overhead
RAID 1 and RAID 10 trade usable efficiency for mirrored protection. They are simpler to reason about, but expensive in raw-capacity terms.
Planning reality
This tool models RAID-level capacity only. Filesystem overhead, vendor reserves, snapshots, and performance behavior are separate decisions.
Related tools
Continue into adjacent storage and infrastructure planning helpers.