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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

  • Total capacity18 TB
  • Interface typeSAS 12Gb/s
  • Form factor3.5 in (8.89 cm)
  • Recommended useFor Enterprise Storage
  • 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.

How it compares

Measured against everything we stock in 3.5-Inch Internal Desktop HDDs, at today’s prices. Recalculated every night.

Price $374.99
Pricier than about 88% of the 4,938 comparable items (median $107.99).
Total capacity 18 TB
Higher than about 93% of the 2,372 comparable items (median 2 TB).
Price per TB $20.83 per TB
Cheaper than about 92% of the 2,365 comparable items (median $62.21 per TB).

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Specifications

Product
Brand nameWestern Digital
Product lineWD Ultrastar
Model nameWD Ultrastar DC HC550
Part numberWUH721818AL5201-0F38352
Total capacity18 TB
Recommended useFor Enterprise Storage
Ports & slots
Interface typeSAS 12Gb/s
Size & build
Form factor3.5 in (8.89 cm)

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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