Western Digital selling 7200RPM HDD as 5400RPM

ARS Technica reports rotational speeds of hard disk drives don't mean anything any more, at least for Western Digital. The site reports various Reddit users discovered that Western Digital is selling 7200RPM HDDs as "5400RPM Class". These disks even identify as 5400RPM via the SMART interface -- but are actually spinning at 7200RPM.

So the first question that pops in your head is probably why it's bad that the consumer is getting a faster product than he or she expects? Well, the problem here is that some users are buying 5400RPM HDDs because they have certain expectations. These disks consume less power and generate less noise and heat than 7200RPM versions. With these "5400RPM Class" disks, this is not the case:

Comparing the data sheets between a 5,400rpm Seagate Barracuda and a "5400 RPM Class" Western Digital Red—which, as tested by audio spectral analysis, actually spins at 7,200rpm—we can see a clear difference in power consumption. The 8TB Red consumes 8.8W to the Barracuda's 5.3W when active, and 800mW to the Barracuda's 250mW when in standby mode. The difference here isn't, for the most part, the brand—when they're spinning at the same actual RPMs, Western Digital's and Seagate's drives consume roughly the same power.

ARS Technica reached out to WD and got to hear that "5400RPM Class" indeed means something different than a spindle speed of 5400RPM:

For select products, Western Digital has published RPM speed within a “class” or “performance class” for numerous years rather than publishing specific spindle speeds. We also fine-tune select hard drive platforms and the related HDD characteristics to create several different variations of such platforms to meet different market or application needs. By doing so, we are able to leverage our economies of scale and pass along those savings to our customers. As with every Western Digital product, our product details, which include power, acoustics and performance (data transfer rate), are tested to meet the specifications provided on the product’s data sheet and marketing collateral.