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Seagate CMR/SMR not stated 3.5in

Seagate Exos X16 12TB

12TB

Model ST12000NM001G

rpm
7,200
MB cache
256
TB/yr
550
yr warranty
5

Exos X16 range, also in 14 TB, 16 TB

Who the Exos X16 12 TB is for

Pick it for raw capacity in a box that lives out of earshot, because 7,200 rpm enterprise drives are built to run flat out all day, every day. You also get five years' warranty, two more than the cheapest NAS lines. Its Backblaze record's good too, with 1.00% AFR across 72,056 drive-years and the whole interval below the 1.40% median for the drives they report.

Watch out for

At 7,200 rpm it's from the louder, warmer class. Fine in a cupboard, less fun on a desk. Seagate's own page doesn't say whether it's CMR or SMR, which is a bit annoying for a drive you'd put in an array.

A 4-bay box full of these gives 36 TB after one drive's worth of parity.

Specifications

Each value links to the Seagate page or datasheet it came from, and "Not published" means the maker doesn't list it there.

Seagate Exos X16 12TB specifications
Capacity 12 TB source for Capacity (seagate.com, opens in new tab)
Spindle speed 7,200 rpm source for Spindle speed (seagate.com, opens in new tab)
Recording technology Not published
Cache 256 MB source for Cache (seagate.com, opens in new tab)
Interface SATA 6Gb/s source for Interface (seagate.com, opens in new tab)
Form factor 3.5in source for Form factor (seagate.com, opens in new tab)
Workload rating 550 TB/yr source for Workload rating (seagate.com, opens in new tab)
MTBF / MTTF 2,500,000 hours source for MTBF / MTTF (seagate.com, opens in new tab)
Warranty 5 years source for Warranty (seagate.com, opens in new tab)

Sources: seagate.com, seagate.com

Failure rate

723 failures in 72,056 drive-years, across the 13,072 that Backblaze runs as ST12000NM001G, works out at 1.00% a year. Its 95% interval is 0.93% to 1.08%, and the whole of that sits below the 1.40% median.

Annualised failure rate and 95% interval, lifetime and the last 4 quarters (the wider the bar, the thinner the data)
Lifetime72,056 drive-yrs 1.00%0.93–1.08
2025 Q313,246 drives 0.93%0.63–1.32
2025 Q413,147 drives 0.93%0.63–1.32
2026 Q113,157 drives 1.02%0.70–1.43
2026 Q213,072 drives 1.35%0.98–1.81

Median lifetime AFR across Backblaze drive models: 1.40%

Source: Backblaze Drive Stats, lifetime to 2026 Q2. Bear in mind that's data-centre use, which is a lot harder on a drive than a home NAS will ever be.