On Mon, Jun 19, 2017 at 12:38 PM, Dominik Psenner <dpsenner@xxxxxxxxx> wrote:
When running a virtualized host for example with virtual box we don't see such an impact. What does virtual box do differently to improve virtualized IO and could that help libvirt/qemu/kvm?
Hello,
I would jump here to try to put some information
Even in virtualbox, at virtual storage chapter
you get:
"
In general, you should avoid IDE unless it is the only controller supported by your guest. Whether you use SATA, SCSI or SAS does not make any real difference. The variety of controllers is only supplied for VirtualBox for compatibility with existing hardware and other hypervisors.
"
In fact, just tried with a not so new version of virtualbox (4.3.6 I don't use it very often), if I create a VM with Windows 2012 as OS, by default it sets the os disk on top of a virtualized sata controller, that should be more efficient.
Or are you saying that you explicitly configured Virtualbox and selected IDE as controller type for the guest?
Indeed I verified that in new version of virt-manager, when you configure a windows 2012 R2 qemu/kvm VM instead, it does set IDE as the controller and so the performance problems you see. Probably you choose the default proposed?
In the past I also tried IDE on vSphere and it had the same performance problems, because it is fully virtualized and unoptimized
You should set SCSI as controller type in my opinion if you have a recent version of libvirt/qemu/kvm
That said, I don't know what is the level of support for W2016 at time with virtio and virtio-scsi drivers.
You can download iso and virtual floppy images here:
The method could be to add a new disk with the desired controller to the guest: virtio or virtio-scsi
Then configure it using iso or vfd images
Then shutdown the guest and set also the boot disk with the same virtio or virtio-scsi controller and try to boot again.
Having installed the drivers it should auto reconfigure (not tried with w2012 and w2016)
If all goes well shutdown guest again and remove the second disk
Also, you can try to install a new guest and change the controller and provide the installation process the vfs image file.
Try it on a test system to see if it works and if it gives you the desired performance.
HIH a little,
Gianluca
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