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Reference charts

The lookup tables, precalculated. Usable capacity for every drive count and layout, watts per component, link speeds against real throughput, rack unit dimensions, and the decimal against binary conversion that explains most missing-capacity questions.

Capacity figures are computed with the same engine behind the RAID calculator, so they are arithmetic you can check.

How these charts are built

Two kinds of table live in this section, and it is worth knowing which you are reading.

Computed tables are generated at build time from the same functions that drive the RAID capacity calculator. The usable capacity chart, the layout matrix in the RAID level comparison, the failure probability tables and the TB against TiB conversion are all arithmetic. They cannot drift out of agreement with the calculators, and you can verify any cell with a pocket calculator and the formulas printed on the page.

Specification tables come from published manufacturer data. Where a vendor does not publish a figure, or where sources disagree, the cell is omitted rather than estimated. A wrong specification on a specification page is the fastest way to lose a reader who came here precisely because they intend to check the numbers.

One deliberate omission. There is no per-model drive failure rate table on this site, because honest per-model figures move every year and any single number is a snapshot rather than a property of the model. What the reliability chart gives you instead is the arithmetic: annualised failure rate against drive count and years, which is the number that actually decides how much parity you need. Published large-fleet AFR for modern 3.5 inch drives runs about 1.0 to 1.6 percent per year and rises past roughly five years of service.

Units are consistent everywhere. Capacity is decimal terabytes, the number printed on the drive label, with binary tebibytes shown alongside where it matters. One TB is 1,000,000,000,000 bytes and one TiB is 1,099,511,627,776, a fixed ratio of 0.909495, which is why every capacity looks 9.05 percent smaller once your operating system reports it.