Western Digital has been hit by a class-action lawsuit over alleged false advertising over some of its WD Red hard drives featuring undocumented DM-SMR (drive-managed shingled magnetic recording), a physical layer data writing technique that maximizes capacity at heavy costs of random write performance, that effectively render the drives unfit for RAID applications that are common with NAS setups. Trouble brewed for Western Digital in April, as a Blocks & Files report exposed presence of SMR on certain popular WD Red drives as an explanation as to why the drives couldn't be added to RAID volumes.

Western Digital initially tried to defend its position by explaining what DM-SMR is, that the standard WD Red has been tested on most SOHO NAS devices, that they're not meant for serious (> 8-drive) NAS setups; and pointing people to their pricier WD Red Pro, or enterprise-segment Ultrastar HDDs, leading to more community backlash. Days later, Western Digital finally came out with a list of its HDDs that use SMR. Bellevue Washington-based Hattis & Lukacs, class-action specialists, are leading the charge against Western Digital, and are inviting aggrieved U.S. residents to join the class.