I have a core I7 with 16gb of ram, a 240gb SSD drive as main drive (Windows Server 2012 R2 Hyper-V Core) and I store the VMs on a cluster store shared via iSCSI Target (also a Windows Server 2012 R2 iSCSI Target). It functions fine not had any problems with it. Been up and running for a month. Hope this helps!
I am not sure if this is pertinent to your situation, I have been playing with upgrades and came across this post at TechRepublic. http://www.techrepublic.com/blog/data-center/tips-for-an-easy-upgrade-from-windows-server-2012-to-windows-server-2012-r2/ I hope it helps you,