I just bought a new 8TB seagate external drive and I want to partition it into two 3TB partitions and a 2TB partition so I can use my old media drives to back up the new giant one instead of having to buy multiple 8TB drives to back it up. The problem is that Disk Utility (ala El CRAPitan) won't let me do that. I first had to reformat under OS X. OK. Done. It would now let me partition. Great. Instead of using the old slide to size system, it had a PIE CHART that only puts sliders on one side of a pie triangle so if you try to resize the largest part to the left, it creates another partition instead (which I don't want it and it shouldn't do, IMO). In any case, after piddling with the controls, I got what looked like 3TB, 3TB and 2TB, but clicking on each revealed small size differences so I manually changed it to 3.0, 3.0 and that left 2.01. OK, fine. I tell it go ahead. It then says "Operation Successful" and I have in front of me two 1.5TB partitions and a 5.0TB partition!!!! WTF!??!?!??! I tried again. Same thing. It WILL NOT create two 3TB partitions and a 2TB partition for reasons only Apple engineers can probably explain. I see no good way around this situation. I'm going to try to boot from my USB key I made that has Mavericks on it and use its disk utility because this one SUCKS. I mean that is ridiculous! It can't even do a basic partition without fracking it up? Come on Apple! Getting rid of RAID controls was bad enough, but this borders on total ineptitude.