Heads up: There appears to be a bad batch of WD20EARS out there. I have now tested the fifth(!!) drive in a row, all of which seem to belong to a batch made in “22 Oct 2010”. All of them, new out of the box, failed the DLGDIAG Extended Test, with “Too many bad sectors”. Apparently my supplier (to whom we are running back and forth for replacements) had a series of them in the warehouse so the replacements I got were coming from the same batch
If you have a WD20EARS marked “22 Oct 2010”, I’d strongly recommend you run the test.
You’d not believe the amount of time we’ve spent on a box we’re building that had 4 of these, chasing all kinds of weird phenomena, not entertaining the “very unlikely” explanation that all those drives were bad.