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Seagate Exos X16 vs X18: which to buy used
Buy whichever generation is cheaper per terabyte at the capacity you need. The Exos X16 and X18 share the same 7200 rpm helium design, 256 MB cache, 550 TB/year rating and 5-year original warranty. The X18 adds an 18 TB model; at 16 TB and below the two are interchangeable in a NAS or ZFS pool.
Updated Nov 3, 2026
Side by side
| Specification | Exos X16 | Exos X18 |
|---|---|---|
| Capacities | 10, 12, 14, 16 TB | 10 to 18 TB |
| Spindle speed | 7200 rpm | 7200 rpm |
| Cache | 256 MB | 256 MB |
| Fill | Helium | Helium |
| Recording | CMR | CMR |
| Interfaces | SATA 6 Gb/s, SAS 12 Gb/s | SATA 6 Gb/s, SAS 12 Gb/s |
| Sector formats | 512e, 4Kn | 512e, 4Kn |
| Max sustained transfer | About 260 MB/s | About 270 MB/s |
| Workload rating | 550 TB/year | 550 TB/year |
| MTBF | 2.5 million hours | 2.5 million hours |
| Power, idle / random load | About 5 W / 9 to 10 W | About 5 W / 9 to 10 W |
| First shipped | 2019 | 2020 |
| Original warranty | 5 years | 5 years |
| Part-number suffix | G (ST16000NM001G) | J (ST18000NM000J) |
- Transfer rates are datasheet maximums for the largest capacity in each family, on the outer tracks. Smaller capacities run a little slower.
- MTBF and power figures are from Seagate datasheets.
Which to pick
Bay-limited server or NAS
Exos X18 18TB
The only 18 TB model in either family. More capacity per bay usually outweighs the higher price.
Budget pool at 16 TB or less
Exos X16
Same platform at the same capacity, and usually cheaper per terabyte because more used units are on the market.
Replacing a drive in an existing array
Either, matched by capacity
A 16 TB X18 replaces a 16 TB X16 without issue. Capacity matters within a vdev; generation does not.
Server with an HBA already installed
SAS version of either
Same mechanics as SATA, and often lower per terabyte because fewer buyers can use SAS.
Our test data and stock
Every unit of these models we have tested in-house, from our test database, and what is listed today.
Exos X16 16TB SAS
ST16000NM002G
1 in stock from $398.96
- Units tested
- 16
- Passed
- 16
- Median hours
- 27,178 h
- Price
- $398.96 to $446.46
Exos X16 14TB SATA
ST14000NM001G
9 in stock from $322.96
- Units tested
- 10
- Passed
- 10
- Median hours
- 17,542 h
- Price
- $322.96
Exos X18 18TB SATA
ST18000NM000J
18 in stock from $417.96
- Units tested
- 28
- Passed
- 28
- Median hours
- 25,568 h
- Price
- $417.96
Exos X18 16TB SATA
ST16000NM000J
1 in stock from $427.46
- Units tested
- 1
- Passed
- 1
- Median hours
- 35,746 h
- Price
- $427.46
Common questions
Is the Exos X18 faster than the X16?+
By about 10 MB/s of sequential transfer on paper, from higher areal density. Inside an array the gap is smaller than normal drive-to-drive variation.
Can X16 and X18 drives share a pool?+
Yes. Keep capacities matched within each vdev or RAID group; mixing generations at the same capacity is fine.
Which used drives tend to have more hours?+
X16 units, since the family started shipping in 2019, a year before the X18. Check the power-on hours and tier of the actual unit rather than assuming the newer family is fresher.
How do I tell X16 and X18 apart by part number?+
The G suffix family is X16 (for example ST16000NM001G) and the J suffix family is X18 (ST18000NM000J). The leading digits are the capacity in GB.