WD Ultrastar vs Red Pro: What WD's NAS and Data Centre Sheets Say at 18TB to 26TB

Ultrastar vs Red Pro: the ratings WD prints for each

People often assume the NAS drive is the lightly rated one. On WD's Red Pro data sheet (2TB to 26TB) that is not so. Every Red Pro model from 18 TB to 26 TB is rated for 550TB/year workloads, carries 2,500,000 hours MTBF and a 5-year limited warranty, and is listed as CMR with 512 MB of cache. Each Ultrastar sheet from the HC550 to the HC590 gives the same workload ceiling and the same warranty term.

That leaves very little for the badge to decide. A Red Pro bought for a NAS and an Ultrastar bought for a server are rated, on WD's own paper, for the same amount of work over the same warranty. Where they differ is per model: Red Pro has two models at 20 TB and two at 24 TB with different figures, and its sheet uses different headings for transfer and power from the Ultrastar sheets.

WD Ultrastar vs Red Pro by model at 18TB to 26TB

Red Pro has seven models across these five sizes. The table gives each with its transfer figure and idle power, beside the Ultrastar generation at the same size. Note the labels: Red Pro prints internal transfer rate (max), Ultrastar prints sustained transfer rate, and WD's two families footnote their idle figures separately.

The 20 TB pair is the one to watch. WD202KFGX prints 285 MB/s and 3.6 W, WD201KFGX 268 MB/s and 3.8 W, so two Red Pro 20TB listings are not interchangeable on paper. At 24 TB the pair shares 287 MB/s but WD240KFGX idles at 3.9 W against 3.6 W on WD241KFGX. The 22 TB WD221KFGX has the lowest transfer figure of the seven, 265 MB/s, and the lowest idle, 3.4 W.

Why the idle columns are not subtracted: every Red Pro figure sits between 3.4 W and 3.9 W and every Ultrastar figure between 5.5 W and 6.1 W, a gap large enough to tempt a conclusion. But the Red Pro sheet prints its power under its own heading and conditions, and the Ultrastar sheets print Idle with a separate footnote. We have not found a document confirming that the two describe the same state, so the gap may be partly a difference in how WD measured. The same caution applies to internal against sustained transfer rate.

Red Pro vs Ultrastar noise: dBA against bels

Red Pro's sheet gives each model an idle figure and an average seek figure in dBA. WD's data centre sheets instead print a typical pair in bels, idle and operating. With no WD document we have found that explains either scale or bridges them, the useful readings are the ones inside the Red Pro sheet, where the 24 TB suffix split shows up again.

Two Red Pro drives at 24 TB, two idle figures: WD240KFGX at 20 dBA and WD241KFGX at 25 dBA, the latter matching the 26 TB model. Seek is 32 dBA on every Red Pro except the 18 TB, at 36. On the Ultrastar side the idle bels hold steady until the HC590; that sheet lists operating before idle, 3.2/2.5, so its idle figure is taken as 2.5 by its own label.

We do not rank Red Pro against Ultrastar on noise. If a quiet Red Pro at 24 TB matters, the sheet answers it inside one document: WD240KFGX at 20 dBA idle, WD241KFGX at 25.

Ultrastar vs Red Pro prices on Amazon.co.uk

Because the ratings are level, price per TB is often the deciding row. Figures are new listings on Amazon.co.uk in pounds sterling inc VAT; where a cell shows a dash, that line has nothing in stock at that capacity at the moment.

The Red Pro list runs across every capacity, including sizes below 18 TB; at 20 TB and 24 TB, match the KFGX number on each row to the model table before trusting its figures. The Ultrastar list mixes SATA with SAS, so the interface column matters, and HC555 and SS530 listings are not in it. A recording technology appears only where a document names the part number.

WD Ultrastar or Red Pro: reading the choice

• Workload, warranty, cache and recording technology do not decide it: both families state 550TB a year, 5 years, 512 MB and CMR.
• Lowest printed idle: Red Pro, from 3.4 W to 3.9 W, with the measuring caveat above.
• Highest printed transfer at 24 TB and 26 TB: Ultrastar, at 298 MB/s on the HC580 and 302 MB/s on the HC590, though Red Pro's figure is an internal rate.
• At 20 TB or 24 TB on the Red Pro side, the model suffix changes the figures, so match it to the table.

The Red Pro family continues on WD Red Pro. On the data centre side, any one generation from the table can be followed further: HC550, HC560, HC570, HC580 or HC590, within WD Ultrastar. WD's SATA enterprise line against Ultrastar is on Ultrastar vs WD Gold.