Your network contains an Active Directory domain named contoso.com. The domain
contains two servers named Server1 and Server2 that run Windows Server 2012 R2.
Server1 is a file server that has the Hyper-V server role installed.
Server1 hosts several virtual machines. The virtual machine configuration files are stored on
drive D and the VHD files are stored on drive E.
You plan to replace drive E with a larger volume.
You need to ensure that the virtual machines on Server1 remain available while drive E is
being replaced.
What should you do?

A.
Perform a quick migration.

B.
Add Server1 and Server2 as nodes in a failover cluster.

C.
Perform a live migration.

D.
Perform a storage migration.

Explanation:
D)
Hyper-V in Windows Server 2012 R2 introduces support for moving virtual machine
storage without downtime by making it possible to move the storage while the virtual
machine remains running.
http://technet.microsoft.com/en-us/library/hh831656.aspx