The reason I ask, is that the two iomega drives (couldn't find a review on any 4 TB externals, and these were middle of the road expensive) are replacing one still working WD 2TB drive, and one dead WD 2TB drive. I had noticed that even with the two drives sync'd for files that the one drive showed almost 1 gig less space than the other. So my presumption is that one was set to a different cluster size than the other. Unfortunately the one drive died before I could figure out why. Not that I had the drive for that short a time, but rather that both drives started out with less than 1 TB a year ago, and only recently as they both neared 1.5TB did I notice the difference.