• Server Core Installation Option
  • Dedicated Server Role
  • Guest Operating Systems
  • CPU Statistics
  • Performance Tuning Guidelines for Windows Server 2012 April 12, 2013 Abstract

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    Server Configuration

    This section describes best practices for selecting hardware for virtualization servers and installing and setting up Windows Server 2012 for the Hyper-V server role.

    Hardware Selection

    The hardware considerations for servers running Hyper-V generally resemble those of non-virtualized servers, but servers running Hyper-V can exhibit increased CPU usage, consume more memory, and need larger I/O bandwidth because of server consolidation. For more information, refer to Choosing and Tuning Server Hardware earlier in this guide.


    Hyper-V in Windows Server 2012 presents the logical processors as one or more virtual processors to each active virtual machine. You can achieve additional run-time efficiency by using processors that support Second Level Address Translation (SLAT) technologies such as Extended Page Tables (EPT) or Nested Page Tables (NPT).


    Hyper-V can benefit from larger processor caches, especially for loads that have a large working set in memory and in virtual machine configurations in which the ratio of virtual processors to logical processors is high.


    The physical server requires sufficient memory for the root and child partitions. Hyper-V first allocates the memory for child partitions, which should be sized based on the needs of the expected load for each virtual machine. Having additional memory available allows the root to efficiently perform I/Os on behalf of the virtual machines and operations such as a virtual machine snapshot.


    If the expected loads are network intensive, the virtualization server can benefit from having multiple network adapters or multiport network adapters. Each network adapter is assigned to its own virtual switch, which enables each virtual switch to service a subset of virtual machines. When you hostmultiple virtual machines, using multiple network adapters enables distribution of the network traffic among the adapters for better overall performance.

    To reduce the CPU usage of network I/Os from virtual machines, Hyper-V can use hardware offloads such as Large Send Offload (LSOv1, LSOv2), TCP checksum offload (TCPv4, TCPv6), and virtual machine queue (VMQ). No further configuration of the guest virtual machine is required. The network adapter provides coalesced packets to the host, and the host passes them along to the destination virtual machine.

    For details about network hardware considerations, see Performance Tuning for the Networking Subsystem earlier in this guide.


    The storage hardware should have sufficient I/O bandwidth and capacity to meet the current and future needs of the virtual machines that the physical server hosts. Consider these requirements when you select storage controllers and disks and choose the RAID configuration. Placing virtual machines with highly disk-intensive workloads on different physical disks will likely improve overall performance. For example, if four virtual machines share a single disk and actively use it, each virtual machine can yield only 25 percent of the bandwidth of that disk. For details about storage hardware considerations and discussion on sizing and RAID selection, see Performance Tuning for the Storage Subsystem earlier in this guide.

    Server Core Installation Option

    Windows Server 2012, Windows Server 2008 R2, and Windows Server 2008 feature the Server Core installation option. Server Core offers a minimal environment for hosting a select set of server roles including Hyper-V. It features a smaller disk, memory profile, and attack surface. Therefore, we highly recommend that Hyper-V virtualization servers use the Server Core installation option.

    A Server Core installation offers a console window only when the user is logged on, but Hyper-V exposes management features through WMI so administrators can manage it remotely. For more information, see Resources later in this guide.

    Dedicated Server Role

    The root partition should be dedicated to the virtualization server role. Additional server roles can adversely affect the performance of the virtualization server, especially if they consume significant CPU, memory, or I/O bandwidth. Minimizing the server roles in the root partition has additional benefits such as reducing the attack surface and the frequency of updates.

    System administrators should consider carefully what software is installed in the root partition because some software can adversely affect the overall performance of the virtualization server.

    Guest Operating Systems

    Hyper-V supports and has been tuned for a number of different guest operating systems. The number of virtual processors that are supported per guest depends on the guest operating system. For a list of the supported guest operating systems, see Hyper-V Overview in the Windows Server Technical Library or the documentation that is provided with Hyper-V.

    CPU Statistics

    Hyper-V publishes performance counters to help characterize the behavior of the virtualization server and report the resource usage. The standard set of tools for viewing performance counters in Windows includes Performance Monitor (Perfmon.exe) and Logman.exe, which can display and log the Hyper-V performance counters. The names of the relevant counter objects are prefixed with “Hyper-V.”

    You should always measure the CPU usage of the physical system by using the Hyper-V Hypervisor Logical Processor performance counters. The CPU utilization counters that Task Manager and Performance Monitor report in the root and child partitions do not accurately capture the CPU usage. Use the following performance counters to monitor performance:

    \Hyper-V Hypervisor Logical Processor (*) \% Total Run Time

    The counter represents the total non-idle time of the logical processor(s).

    \Hyper-V Hypervisor Logical Processor (*) \% Guest Run Time

    The counter represents the time spent running cycles within a guest or within the host.

    \Hyper-V Hypervisor Logical Processor (*) \% Hypervisor Run Time

    The counter represents the time spent running within the hypervisor.

    \Hyper-V Hypervisor Root Virtual Processor (*) \ *

    The counters measure the CPU usage of the root partition.

    \Hyper-V Hypervisor Virtual Processor (*) \ *

    The counters measure the CPU usage of guest partitions.

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    Performance Tuning Guidelines for Windows Server 2012 April 12, 2013 Abstract

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