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Standard 3.5-inch enterprise hard drive with silver metal casing and SAS connector

Western Digital

Western Digital Ultrastar DC HC550 18TB SAS 12Gb/s 7200RPM 3.5" internal hard drive

SKU CH-KXH2-D2A40

An 18 TB enterprise hard drive with a SAS 12Gb/s interface, 7200 RPM speed and helium-sealed CMR technology for high-density data-centre storage

  • InterfaceSAS 12Gb/s
  • Capacity18TB
  • UsageFor Enterprise Storage
  • Form Factor3.5"
  • 18 TB capacity in a standard 3.5 inch form factor
  • SAS 12 Gb/s interface built for enterprise storage systems
  • CMR technology supports all capacity enterprise workloads
  • 5 million hours projected MTBF for high reliability
  • Helium sealed design lowers power per TB by 21 percent

Enterprise Capacity and Interface

The Western Digital Ultrastar DC HC550 is an 18TB 3.5-inch internal hard drive built for enterprise storage environments. It uses a SAS 12Gb/s interface and conventional magnetic recording technology. The drive spins at 7200RPM and carries a projected 2.5M hours MTBF rating. It is designed for cloud, hyperscale and massive scale-out data centres rather than desktop PCs.

Density Upgrade From Lower Capacities

An 18TB drive provides 29% more capacity in the same form factor as a 14TB model. This density increase lets operators reduce supporting hardware, cutting required rack count by 22%. The jump is worth it when total cost of ownership drives the architecture and bulk storage workloads demand maximum terabytes per slot. Buyers needing less capacity or a desktop interface should consider other options.

Sustained Operation in Dense Deployments

Helium sealing lowers power draw, delivering 21% less power per terabyte at idle compared to 14TB drives. The 6th generation design targets reliable performance in distributed file systems, object storage and big data analytics clusters. Energy-assisted magnetic recording supports consistent write throughput across the full 18TB. The drive is built for continuous operation in high-density racks, not for intermittent client workloads.

Highlights

  • 18 TB capacity in a standard 3.5 inch form factor
  • SAS 12 Gb/s interface built for enterprise storage systems
  • CMR technology supports all capacity enterprise workloads
  • 5 million hours projected MTBF for high reliability
  • Helium sealed design lowers power per TB by 21 percent

Specifications

BrandWestern Digital
SeriesWD Ultrastar
ModelWD Ultrastar DC HC550
Part NumberWUH721818AL5201-0F38352
InterfaceSAS 12Gb/s
Capacity18TB
UsageFor Enterprise Storage
Form Factor3.5"

Questions about this item

What 3.5-inch drive bay and SAS backplane does the WUH721818AL5201 need?

It fits a standard 3.5-inch bay and connects to a 12Gb/s SAS backplane; the helium-sealed chassis requires no extra mounting hardware beyond the bay screws.

Which step is often missed when installing the WUH721818AL5201 in a RAID array?

After cabling the SAS 12Gb/s links, the drive must be initialized in the RAID controller BIOS before the operating system sees the 18TB volume.

When should the helium-sealed WUH721818AL5201 be retired under a 2.5M-hour MTBF plan?

With a 2.5M-hour MTBF rating, most data centers schedule replacement on a 5-to-7-year refresh cycle rather than wait for a predicted failure.

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