If you consider a 2x area increase going from a 3.5->5.25, and another 4x going from a 3.5" HH to a 5.25 FH, your talking a 8x capacity increase. That is ballpa

If you consider a 2x area increase going from a 3.5->5.25, and another 4x going from a 3.5" HH to a 5.25 FH, your talking a 8x capacity increase. That is ballpark over 100TB in a 5.25" drive bay. 5 of those standing vertical would fit in a 19" rack for ~600TB in the front panel. Of course a 3U is exactly 5.25", so you would have to modify the original form factor a bit to make it fit or use 4U and waste a half inch. Bottom line, assuming 20T 3.5" drives, you have doubled the front capacity of a 3U case. OTOH, if you really wanted to play games consider how much capacity could be stored on a 19" platter like the old IBM mainframe disk units.