Is it possible to convert to Virtio?

ozgurerdogan

Renowned Member
May 2, 2010
604
5
83
Bursa, Turkey, Turkey
Hello
Is it possible to convert a running system's disk from BUS to Virtio for KVM and windows 2008?

If not, would be possible to install a new windows 2008 box with virtio disk and clone other 2008 which has BUS to Virtio one you think?

Thanks
 
With "BUS" you mean IDE I suppose. Yes, it's possible, just you could risk that Win2008 ask you for a reactivation (hardware change can trigger it).
Sure on the wiki you find the answer, that is the same way you usually follow when installing as Virtio from the beginning.
In short, shutdown Win2008 and simply add a very small HD (like 1GB) with Virtio type to your Win2008 guest from web interface, and have the cdrom pointing to the ISO with the virtio drivers for kvm (latest and greatests, virtio-win-1.1.11-0.iso at the moment, see http://alt.fedoraproject.org/pub/alt/virtio-win/latest/images/bin/).
Boot Win2008 that will detect the new 1GB HD and ask you for drivers. Install them (the ones in P { margin-bottom: 0cm; }'Wlh' dir on the .iso) and shutdown. Remove the additional hd AND your current HD (will be listed beyond as unused HD), and then re-add it picking it from the unused section, but this time with VIRTIO interface. Boot the VM and enjoy!
Of course, I don't take resposability for the success of the above, so do a backup first, just in case...
 
I already read wiki but too much work makes me sometimes forget things quickly:) I converted all disk to virtio. Will see performance difference now. I hope there is reasonable performance using virtio.

Thanks
 
Please, report back your findings, I'm interested too. I think the opposite side of performance are, on the lowest end, qcow file based VM with IDE drivers, and at the highest level with LVM storage with virtio, but I don't know how much each element counts (i.e. file based raw against qcow? virtio raw file vs ide raw file? lvw raw vs file raw?). Also consider that for lvm storage you can disable vm cache for further gain.
 
I do not expect a big difference. But a reasonable difference is ok. And I guess some applications are little better performing now. Bad site, I am not using lvm storage only local harddrives.
 
I know it is an old thread but just to confirm my findings:
I ran iometer on XP with IDE disks, it gave me iops of ~250 / 300 and a max of 4.5Megabyte p/s disk r/w speed.
I converted the disk to virtio like said above and ran iometer again and now disk r/w is around 50Megabyte p/s so this is a big difference!
 
Just to update the assembled company as to a potential change in the way Win 2008 handles all this with a fully updated Win2008R2 VM.

I booted the VM with the prescribed secondary 1GB VirtIO drive, but the boot sequence didn't recognise any changes. I then went to the device manager and found an unregistered device. I opened it up and added a new driver from the virtio virtual floppy. It then happily recognised the new drive. From there it was exactly as above .. shut the machine down, remove the dummy secondary, delete the IDE main drive, add the same virtual hard drive as a virtio drive and reboot.

The same sort of tweak worked nicely for the VirtIO network driver, which gained us at least 3x speed increase.

Subtle differences notwithstanding, thanks very much for the thread.

Andy M
 

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