Home server calculators

Search for a RAID calculator and every result belongs to somebody who sells storage. Synology's tool models SHR. TrueNAS-adjacent tools model RAIDZ. Controller vendors model the classic levels. Each is accurate about its own scheme and silent about the others, so the one comparison a buyer actually needs, the same physical drives evaluated under every layout at once, does not exist on any manufacturer site.

That gap matters most exactly where the money is. Mixed drive sizes are where Synology SHR pulls ahead, because it slices the drives into horizontal bands and protects each band separately, while standard RAID and every ZFS vdev truncate each member down to the smallest drive and strand the difference. A vendor tool will not show you the size of what you are stranding. Ours does, on the RAID capacity calculator.

The other tools here exist because storage decisions have consequences that arrive later. Power draw is a bill you pay every month for as long as the array runs. UPS runtime decides whether an outage during a write is an inconvenience or a rebuild. Drive failure probability turns an annualised failure rate into the number that matters, which is the odds across every drive you own over several years. And backup sizing exists because RAID is not a backup and the array is only copy one.

Two accuracy notes that apply to everything on this site. First, all capacity figures are decimal terabytes, the number printed on the drive label, with binary tebibytes shown alongside; the fixed 9.05 percent difference between them explains almost every "where did my capacity go" question. Second, the unrecoverable read error figures used in rebuild-risk estimates come from manufacturer warranty floors rather than measurements, and observed rates across large fleets run substantially better. Use them to rank layouts against each other, never as a forecast that your rebuild will fail.

Every calculator here is researched guidance built from published specifications and standard formulas, not professional data recovery or electrical advice. Verify capacity and power figures against your own manufacturer documentation, keep verified backups regardless of what any tool tells you, and have mains wiring done by a licensed electrician.