CPU Utilization Question

[tow-eric]

Hi, I have a 4 host ESX 3.5 environment with DRS and HA running. The hosts are blades in an HP BL25 enclosure. They have 2 dual core AMD Opteron 1.8ghz Processors and all are loaded with 16gb of memory. One of my VM's shows it's average CPU usage as 96%. The host that this VM is running is only using 27% of the CPU for the host. So it is weird that the VM's CPU is pegging but it looks like there is more then enough CPU available on the host?

This VM is a Windows 2003 server that is running some security camera software which records and collects data on a separate RDM attached to this VM. I am wondering if there is anything I can try to get the CPU usage to go drop? We have about 25 VM's total on the 4 hosts. We do not use resource pools at all.

Any help would be great.

Thanks.

[happyhammer]

how many vCPU's does teh VM have configured ?

if the VM has only 1 vCPU then it will only be able to use the Equivilant of 1 cpu and will not start using an accumulation of all cpu's on the host.

[tow-eric]

Currently it only has 1 vCPU. I was told that most of the time 1 vCPU would be fine and that only VM's that can utilize more then 1 proc will benefit from changing to 2 or 4 vCPU's? Should I try changing this to 2 vCPU's?

Thanks.

[mikepodoherty]

Actually, this doesn't sound like a vCPU issue - the application is using 96% of the CPU assigned to it and this works out to 27% CPU usage on the host server. I'd upgrade to 2vCPUs only if there is documentation that shows that the application benefits from 2 CPUs. Otherwise, I'd look into why the application requires so much processing power.

[mikepodoherty]

Forgot to ask - was this server built as a Virtual Server or convereted from a physical server/?

If it was converted, then I suggest checking to make sure the process was reset to a single processor under device manager and checking to see if any non-used hardware (phantom hardware) still is seen in device manager - if so, cleaning up the phantom hardware and updating the processor information to single processor whould help.

[tow-eric]

This was built as a VM. I just changed the vCPU to see if that will have any affect. Luckily not to many people are using this yet, so I will have some room to shut it down when I want for the next few days.

[hstagner]

Hello tow-eric,

Keep in mind that when you use 2 vCPUs that VM's processing time must be scheduled on two physical cores simultaneously. This means that when the 2 vCPU VM is processing, the other VMs on the system are left with only 2 cores to work with.

Like others have said, only do 2 vCPU VM's if the application can genuinely benefit from it. It is much harder on a Windows machine to go back to a single CPU HAL than it is to go forward to a multi-CPU HAL. I hope this helps.

Don't forget to use the buttons on the side to award points if you found this useful (you'll get points too).

Regards,

Harley Stagner

[tow-eric]

It is odd because ever since I moved it to 2 vCPU's the usage has stayed between 50% - 70% and hasn't pegged yet.

So are you saying if I wanted to go back and change it to 1 vCPU to see if it spikes again, the OS would have issues with it?

[mikepodoherty]

IF you go back to 1 vCPU, you would need to update the processor information in device manger to roll that back to single processor or you will have issues.

Don't be surprized is the utilization pegs occassionally - that's normal.

If it goes back up to 96% all the time, then I'd be concerned.

[tow-eric]

What would I need to updated in device manager? I think I have rolled back to 1vCPU before and never did anything in device manager?

[hstagner]

Hello tow-eric,

Have a look at this guide for using VMware Converter . At the end there is a section called "What should I do after I successfully convert my virtual machine". In this section, it goes over replacing the HAL. I hope this helps.

Don't forget to use the buttons on the side to award points if you found this useful (you'll get points too).

Regards,

Harley Stagner

[RParker]

> So are you saying if I wanted to go back and change it to 1 vCPU to see if it spikes again, the OS would have issues with it?

I don't see where you identified what process in the VM is causing the CPU spike in the first place. What specific process is spiking the usage in task manager? I suspect you could have a virus...

[tow-eric]

The process is the application the server is using for recording video and storing it. No roque processess or anything.

I haven't tried reverting back to 1vCPU, but will and let you know the results.

Thanks.

[RParker]

> I haven't tried reverting back to 1vCPU, but will and let you know the results.

don't forget the HAL! Going from 1 CPU to 2 CPU is easy, plug and pray will take care of that, however, going from multi to uni hal is somewhat of a chore.. you have to right click the driver and choose one and HOPE it will detect you can use uni.. if it doesn't.. well that's an entire thread unto itself.

http://support.microsoft.com/kb/299340

[tow-eric]

Just changed it back to 1 vCPU and changed the processor to Uni. Everything came back fine. But now the CPU is back being pegged. So it looks like 2 vCPU's it is!