Seagate Exos X18 18TB
18TB
Model ST18000NM000J
- rpm
- 7,200
- MB cache
- 256
- TB/yr
- 550
- yr warranty
- 5
Exos X18 range
Should you buy the Exos X18 18 TB?
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. Five years of warranty is the other draw, and on a drive you'll leave spinning for most of a decade that's worth having. It's CMR, which is what you want anywhere near a RAID or ZFS rebuild.
Watch out for
Being 7,200 rpm, it's in the noisier, warmer class of drive, and you'll want it somewhere you don't sit. Its Backblaze record is the weak spot, with 3.17% AFR and even the bottom of the interval above the 1.40% median.
A 4-bay box full of these gives 54 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.
| Capacity | 18 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 | CMR | source for Recording technology (seagate.com, opens in new tab) |
| 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
11 failures in 347 drive-years, across the 66 that Backblaze runs as ST18000NM000J, works out at 3.17% a year. Its 95% interval is 1.58% to 5.67%, and even the bottom of that is over the 1.40% median.
Lifetime347 drive-yrs 3.17%1.58–5.67
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.
Seagate Exos X18 18TBST18000NM000J