I have been using WD’s 2TB, 4TB and 6TB My Book Raid external drives since each appeared (many years now, in the case of the 2TB). I have not had any problems with any of them configured as RAID 1 except about once a month I get a red blinking WD in my menubar and the dire red dot warning that one of the drives failed and I should launch WD Drive Manager. When I do that I get a dialog saying the drive failed and there is no solution and to call WD. Oh heavens! A few minutes later the red dot turns to green, the blinking red menu bar icon turns green and everything works and the drive is listed as Healthy. Copying to and from the drive works normally.
I’m writing this so others may benefit: don’t panic right away when WD software burps a warning. Sure, your drive may have indeed failed - just don’t depend on WD Drive Manager’s initial assessment.