The Performance Tuning Guidelines for Windows Server 2008 has been updated to include perf guidelines for virtualization servers. It also gives the following advice for perftuning your VMs in order to save an additional percent or two of perf:

Minimizing the background activity in idle VMs releases CPU cycles that can be used elsewhere by other VMs or saved to reduce power consumption. Windows guests typically use less than 1 percent of one CPU when they are idle. The following are several best practices for minimizing the background CPU usage of a VM:

· Install the latest version of VM integration services.

· Remove the emulated network adapter through the VM settings dialog box (use a synthetic adapter).

· Disable the screen saver or select a blank screen saver.

· Remove unused devices such as the CD-ROM and COM port, or disconnect their media.

· Keep the Windows guest at the logon screen when it is not being used (and disable its screen saver).

· Use Windows Server 2008 for the guest operating system.

· Disable, throttle, or stagger periodic activity such as backup and defragmentation if appropriate.

· Review scheduled tasks and services enabled by default.

· Improve server applications to reduce periodic activity (such as timers).

The following are additional best practices for configuring a client version of Windows in a VM to reduce the overall CPU usage:

· Disable background services such as SuperFetch and Windows Search.

· Disable scheduled tasks such as Scheduled Defrag.

· Disable AeroGlass and other user interface effects (through the System application in Control Panel).