Western Digital WUH721818ALE6L4 18TB 7200RPM SATA 6Gb/s 3.5in Ultrastar DC HC550 Hard Drive

The Western Digital WUH721818ALE6L4, WD part number 0F38459, is the 18TB SATA version of the Ultrastar DC HC550. It is the top capacity in the HC550 range: a helium-sealed, nine-disk, 3.5-inch drive spinning at 7200 RPM with a 512MB buffer. WD uses energy-assisted magnetic recording and a triple-stage actuator to reach 18TB while staying on conventional magnetic recording (CMR).

For storage planners the appeal is density and power. WD's data sheet gives 5.6W at idle for the SATA models, which works out to about 0.31W per terabyte at 18TB, along with a sustained transfer rate of up to 269 MB/s, a workload rating of up to 550TB per year and a projected MTBF of 2.5 million hours. It fits nearline jobs such as backup repositories, object and scale-out file storage, media libraries and cold or warm tiers in a tiered array. For high-IOPS work, 10K or 15K SAS drives or SSDs remain the right tool.

This exact model is 512e SATA 6Gb/s with the legacy pin 3 layout (no Power Disable) and Base (SE) security, meaning no encryption and sanitize overwrite only. WD sells a separate SED model, WUH721818ALE6L1, and separate 12Gb/s SAS models for dual-port designs. A SATA drive normally runs behind a SAS HBA or RAID controller, but it will not provide dual-path failover in a dual-controller shelf.

Before you order:

• Confirm your controller, enclosure and NAS firmware list 18TB drives.
• Plan the tray. The drive ships bare, and OEM servers from HPE or Dell need their own carrier and may flag drives without OEM firmware.
• Keep sector format and capacity consistent within each RAID group or storage pool.
• Decide on encryption first, since SE and SED are different part numbers.