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Western Digital · Data-centre drive · WUH721818ALE6L4

WD Ultrastar DC HC550 18TB

An enterprise drive. Don't let that put you off, as it's the same 3.5in SATA as a NAS drive and fits the same bays.

Capacity
18 TB
Recording
CMR
Speed
7,200 rpm
Warranty
5 years
Workload
550 TB/yr
Failure rate
No failure data

Good for

  • Busy arrays (550 TB a year)
  • Big media libraries
  • RAID, SHR and ZFS rebuilds
  • 5 years' warranty

Not for

  • A desk or bedroom (7,200 rpm is the louder class)

Updated 27 Oct 2026 · Method 2.0

Should you buy the WD Ultrastar DC HC550 18 TB?

It's at home in a rack or a garage, where 7,200 rpm of spinning rust can whirr away all day without bothering anyone. Five years of warranty is the other draw, and on a drive you'll leave spinning for most of a decade that's worth having. It's CMR, which is what you want anywhere near a RAID or ZFS rebuild.

Watch out for

It's a 7,200 rpm drive and you'll hear it working.

No Backblaze failure rate for this one. They don't run enough of them, if any, for a figure worth quoting. On paper it makes 20 dB at idle and 36 dB seeking. WD lists 5.6 W at idle and 6.5 W working, which comes to 49 kWh a year for a drive that idles around the clock. Four of them in SHR or RAID 5 give 54 TB usable, or 49.1 TB once Windows has done its binary maths on it.

Specifications

Each value links to the Western Digital page or datasheet it came from.

WD Ultrastar DC HC550 18TB specifications
Drive type Data centre source for Drive type (documents.westerndigital.com, opens in new tab)
Capacity 18 TB source for Capacity (documents.westerndigital.com, opens in new tab)
Spindle speed 7,200 rpm source for Spindle speed (documents.westerndigital.com, opens in new tab)
Recording technology CMR source for Recording technology (documents.westerndigital.com, opens in new tab)
Cache 512 MB source for Cache (documents.westerndigital.com, opens in new tab)
Interface SATA 6Gb/s source for Interface (documents.westerndigital.com, opens in new tab)
Form factor 3.5in source for Form factor (documents.westerndigital.com, opens in new tab)
Max sustained transfer 269 MB/s source for Max sustained transfer (documents.westerndigital.com, opens in new tab)
Workload rating 550 TB/yr source for Workload rating (documents.westerndigital.com, opens in new tab)
MTBF / MTTF 2,500,000 hours source for MTBF / MTTF (documents.westerndigital.com, opens in new tab)
Maker's rated AFR 0.35% source for Maker's rated AFR (documents.westerndigital.com, opens in new tab)
Warranty 5 years source for Warranty (documents.westerndigital.com, opens in new tab)
Power at idle 5.6 W source for Power at idle (documents.westerndigital.com, opens in new tab)
Power in use 6.5 W source for Power in use (documents.westerndigital.com, opens in new tab)
Noise at idle 20 dB source for Noise at idle (documents.westerndigital.com, opens in new tab)
Noise when seeking 36 dB source for Noise when seeking (documents.westerndigital.com, opens in new tab)

Sources: documents.westerndigital.com