Disk Management in Windows 2012 R2, where is it?
Solution 1:
Run diskmgmt.msc
just like previous versions of Windows.
Solution 2:
It is really easy to get to by default. You will probably even be a bit annoyed you didn't notice it.
Simply right-click on the Windows logo button. Then start the Computer Management. Most of the other common tools you use for managing your system are also linked there.