The KB article that I reported on was incorrect. I’ve since posted a correction that shows you what the KB article should have said.
Changes and improvements in Windows Hyper-V Server 2012 no longer support pass-through disks if Live Migration is to be used.
I, for one, applaud this. I’ve been quite vocal about disliking passthrough disks. If you need the flexibility and the fastest storage performance then use fixed virtual hard disks. A fixed virtual hard disk is almost the same speed as the underlying LUN and you’re probably getting lots of IOPS by stacking disks in a LUN or disk group. Half the Internet (if not more) runs like this, so stop thinking that your mission critical app for 100 users needs to be special – especially if you’re guessing … and I know you haven’t done an assessment. You know who you are.