Seagate ST18000NM000J 18TB 7200RPM SATA 6Gb/s 3.5in Exos X18 Hard Drive

The Seagate ST18000NM000J is the 18TB SATA drive from the Exos X18 line. It is a helium-sealed, 7200 RPM, 3.5-inch nearline hard drive with a 256MB cache, and Seagate's data sheet confirms it uses conventional magnetic recording (CMR), not shingled recording. That matters for RAID rebuilds and for NAS or ZFS pools, where CMR drives behave predictably under sustained writes.

Seagate lists a maximum sustained transfer rate of 270 MB/s and an MTBF of 2.5 million hours, with a rated workload of up to 550TB per year in the product manual. In practice this is a drive for bulk capacity: backup repositories, media archives, object storage nodes, scale-out file systems and high-density RAID storage. It is not meant to replace 10K or 15K SAS drives in transaction-heavy tiers, where seek time and IOPS matter more than cost per terabyte.

The ST18000NM000J has a single-port SATA 6Gb/s interface. It will run on SATA ports and behind most SAS HBAs and RAID controllers, which also accept SATA drives. If you need dual-port SAS for a dual-controller shelf, the SAS model of this drive is ST18000NM004J. The drive ships in 512e format. Seagate's FastFormat routine can switch it to 4Kn, and that process wipes the drive.

This listing is for the bare drive only. Check the following before you order:

• Bay size and tray: standard 3.5-inch, 26.1mm high. Hot-swap bays need a tray from the chassis maker.
• HPE and Dell servers expect drives in OEM carriers and may report third-party firmware as unsupported.
• Encryption: this is the standard model. The SED version is ST18000NM001J.
• Power and cooling: Seagate lists about 5.3W at idle and up to 9.4W under random load per drive.