Windows – What’s causing CPU utilization 100% during night time

Windows 2003 SP1 went out of support in April, so your OS does not get any security patches anymore. You need to upgrade to SP2 ASAP.

SP2 also has lots of random bug fixes in it - your issue could go away.

If your OS has that old a patch level, there is a good chance some drivers - specifically print drivers - could be out of date on the box too. As drivers are a big source of system instability in general, I would try checking they are all signed and up to date. Having a dodgy print driver would explain why it affects both virtual and physical boxes, and appears to occur randomly regardless of load.

Oh and FYI Citrix 4 goes EOM (End of Maintenance, no more bug fixes) at the end of this month June 09, and EOL (End of Life, no more security patches or any other patches) at the end of Dec 09. Enjoy your upgrade cycle!

First, you have to remember that in Hyper-V that the "host" is called a parent partition and it really just like a virtualized guest with special permissions and roles. Just like any other child/guest, when you open up Task Manager, you can not see the CPU usage of the other children on the server.

Ben Armstrong has a good explanation of this here: http://blogs.msdn.com/virtual_pc_guy/archive/2008/02/28/hyper-v-virtual-machine-cpu-usage-and-task-manager.aspx

To summarize his post, you need to check three things to get an accurate picture of CPU utilization:

1. View the CPU usage on each guest - this is available through Hyper-V Manager or Performance Monitor.

2. CPU usage due to context switching - this is the perfmon counter called % Hypervisor Run Time under Hyper-V Hypervisor Virtual Processor

3. Child partition worker process - vmwp.exe running on the parent partition (1 per child). This handles Hyper-V operations like saving state.