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Engineering tools

Storage calculators

Conversions and ideal capacity estimates with explicit units and assumptions. No device measurements or reliability predictions.

TBW and DWPD

600 TBW / (1 TB × 1,825 days) = 0.328767 DWPD.

DWPD = TBW / (capacity in TB × days). Reverse the equation for TBW. Five 365-day years equal 1,825 days; enter the actual stated rating period.

These are host-write rating conversions, not estimates of NAND writes, remaining life or failure probability. The rated workload and warranty conditions still matter. Dataset and method.

Ideal transfer time

1 TB at 100 MB/s = 10,000 seconds (2.777778 hours).

seconds = bytes / bytes per second. TB and MB are decimal; TiB and MiB use powers of two. Gbit/s is decimal bits per second, divided by eight.

Assumes a constant useful transfer rate. Protocol overhead, small files, contention, seek time, retries, cache exhaustion and verification can increase elapsed time. A link's advertised rate is not necessarily its useful throughput.

Ideal RAID capacity

6 active drives in RAID 6: 32 TB (29.103830 TiB), before filesystem overhead.

For n = installed drives − dedicated spares and smallest-drive capacity s: RAID 0 uses n × s, RAID 1 uses s, RAID 5 uses (n − 1) × s, RAID 6 uses (n − 2) × s, and RAID 10 uses (n / 2) × s.

RAID 1 means one n-way mirror. RAID 10 means an even number of active drives in two-way mirrors. Excludes filesystem metadata, reserved space, compression and vendor-specific layouts. RAID 0 provides no redundancy; none of these results is a backup or durability guarantee. Rebuild risks and assumptions.