Hyper-V virtual machine at 100% CPU inexlicably

In some cases, I've seen Hyper-V virtual machines run at 100% CPU usage.  I can't explain it - but the cause is Windows Update on the VM itself.  The fix is to disable the Windows Update service from automatic startup and stop the service.  This fixes the problem.  You'd need to install updates manually going forward.

Moving Hyper-V from Windows 2008 R2 to Windows Server 2012 R2

You can't import a virtual machine created on Windows 2008 R2 into a server running Windows 2012 R2.  There's some aspect that's incompatible.

Here's what worked best for me:

Stop the old VM on the Win 2008 R2 machine
Copy the VHD file to the Win 2012 R2 machine
Create a new virtual machine and tell it to connect to an existing virtual disk
Choose the VHD you moved

If you get error 0×80070569 like I did when you try to complete the new VM wizard, restart the Hyper-V Virtual Machine Management per this page:
http://www.wolffhaven45.com/blog/hyper-v/hyper-v-error-0x80070569/

Increasing the size of Hyper-V virtual disk on Win 2008 R2

I had to increase the size of a virtual machine on a Windows 2008 R2 host.  I'd go to the settings of the VM and click on "edit" would be greyed out when attempting to edit the hard drive size.  It looked like this.

I needed to do three things to resize the disk:
1) shut down the VM
2) Delete all the snapshots of the VM
3) Let the VM merge itself to all previous snapshots - see this

It can take minutes or hours for the merge (#3 above) to take effect.

After the merge has taken place, you can increase the size of the disk and then you'll need to extend the size of the hard drive within Windows of the VM:

Snapshots taking up tons of space on VM host machines

I found myself in a situation where I had a 1 TB drive on a VM host (running Windows 2008 R2) with four virtual machines on it that was completely out of space.  I found that there were tons of AVHD files taking up a lot of room.  Per what I read, these are snapshot files, even though I deleted the snap shots from the Hyper-V Manager (and cleared up a dozen GB or so), the snapshots were not truly gone.

This page talks a little bit about the process:

http://blogs.msdn.com/b/charles_sterling/archive/2008/08/06/what-are-all-these-avhd-files-hyper-v.aspx?Redirected=true

But in the end, I got the space back by just turning off the virtual machines.  When I did so, there was a merge process that went on with the snapshots.  In a turned off machine, this just happens automatically.  In the end, I turned off the machines and left them off until the "cancel merge in progress" went away.  For my largest VM (approx 400 GB of storage), this took about 4 hours.

This is what the cancel merge in progress looks like:

backing up a virtual machine to a local USB hard drive

A virtual machine can't natively see USB hard drives. The USB hard drives are attached to the host OS and not visible by the virtual machine. I wondered how to get a virtual machine created in Hyper-V to see a local USB drive and I found this excellent tutorial:

http://blog.ronnypot.nl/?p=721

A summary:

In the host OS, go to disk management and take the USB drive offline (right click on it and choose offline)

Shut down the virtual machine you want the USB drive to attach to.

Open the settings for that virual machine

Go to SCSI controller -> hard drive

Under phsyical hard disk, select the USB drive, which should be visible there

Now you'll be able to see the USB drive in the virtual machine and back up to it if that's what you'd like to do.

turning on virtualization assistance in the BIOS

I built my first virtual servers this week, which I will write about later. There was one trick that got me at first.

In this case, I'm using Hyper-V in Windows Server 2008 R2 on a Dell PowerEdge T310.

When I started the first VM, the system told me the hypervisor was not running. One of the things the error told me was that I should make sure that virtualization assistance was enabled in the BIOS. First, I made sure that virtualization was supported for my processor - a Xeon X3430 - which it was. Then I went into the BIOS and found indeed that virtualization was turned off.

After that, I was ready to go.