If you are using Microsoft Hyper-V with new Intel Sandy Bridge or Intel Westmere processors and our server has over 48GB of physical RAM you may get a performance decrease. Microsoft released a hotfix (KB2517329) for this problem.
This could also be a problem with a lot of Hyper-V installations on Cisco UCS, because the most of them will use more than 48GB of memory.
The performance decrease could show its self in the the following issues:
- The CPU usage is high and the server responds slowly when you copy large files on the computer. For example, you copy a 10-GB file
- The disk I/O performance of the virtual machines (VMs) is slow
- Windows takes a long time to start
The hotfix is not include in Service Pack 1 for Hpyer-V R2 or Windows Server 2008 R2.
For more information about this you can check KB2517329