0TS1931: Western Digital Ultrastar DC HC550 18TB 7200 RPM SATA 6Gb/s 512e 3.5-Inch Enterprise Hard Drive

Also listed as: WUH721818ALE6L4, Ultrastar DC HC550 18TB SATA, 0TS1932 · made by Western Digital

The Western Digital Ultrastar DC HC550 18TB (model WUH721818ALE6L4) is a flagship 9-disk helium platform hard drive providing massive storage capacity for software-defined storage, Ceph clusters, and enterprise backup systems. With HelioSeal hermetic sealing, it provides outstanding power efficiency and up to 269 MB/s transfer rates. Second-hand market purchasers should verify SMART helium level health, ensure no reallocated sectors are reported, and check that the 3.5-inch mounting holes align with target server drive sleds.

Specifications

About the 0TS1931

0TS1931 is Western Digital's high-capacity 18TB 7200 RPM SATA 6Gb/s enterprise hard drive in the Ultrastar DC HC550 product line, model WUH721818ALE6L4. Featuring a 9-disk HelioSeal platform with Energy-Assisted Magnetic Recording (EAMR), it provides up to 269 MB/s sustained transfer rates for hyperscale cloud data centers, Ceph storage clusters, and enterprise backup targets. It represents the top capacity tier of the HC550 family.

Compatibility

Compatible with 3.5-inch enterprise server drive bays and multi-bay JBOD disk shelves. Connects to native SATA 6Gb/s ports or SAS/SATA RAID controllers. It does not fit 2.5-inch drive cages. Verify that server backplane power connectors comply with SATA revision 3.3 power disable pin specifications to avoid drive power-up issues with legacy cables.

How to identify a genuine unit

The top label displays Ultrastar DC HC550 branding, Western Digital model WUH721818ALE6L4, part number 0TS1931, and 18TB capacity notation. In Linux dmesg and lsscsi, the drive identifies as WDC WUH721818ALE6L4 with standard Western Digital factory firmware and standard 512e sector geometry.

Buying used

Query smartctl -a to inspect reallocated sector counts, power-on hours, and helium integrity flags. Lightly used pulls from cloud storage nodes often carry clean SMART tables and provide substantial cost savings over new retail drives. Check that the metal top cover is free of dents.

Reference prices (last 14 days, updated 2026-10-27)

Prices seen on public listings on the dates shown, before tax and shipping. Not an offer.

Fits these models

• Lenovo ThinkSystem SR650 V2
• Lenovo ThinkSystem DE4000H

Equivalent part numbers

• Lenovo 4XB7A38130 ThinkSystem 3.5 18TB 7.2K SATA 6Gb Hot Swap HDD

FAQ

Sources

• Ultrastar DC HC550 Hard Drive Data Sheet, checked 2026-10-27