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I am thinking of either running MSSQL 2008 on a bare metal machine or in a Ubuntu Guest based KVM virtual machine. The server itself is quite well provisioned.

I want to use KVM, but my primary concern is the disk I/O - directly vs through the KVM based VM.

Does anyone know:

  1. If the I/O performance is comparable?
  2. Are there any drivers that make win 2008 perform better on a KVM or are these already part of the KVM base virtualization?
  3. Any tools/scripts/command I can run to compare my bare metal I/O thoughput to that via the VM.

Any other advise would be welcome...relatively new to this :)


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  1. Performance is not 100% the speed of the disk subsystem, but pretty close if you avoid overhead. In general, it is recommended to use raw, preallocated images, and use qcow2 only for snapshots.
  2. Virtio drivers can make the VM go much faster. They are available from
  3. iozone comes to mind

I have seen ubuntu and gentoo act weird with kvm, which has been fixed by a reinstall of the right packages. Never seen the same on fedora or RHEL though - everything works out of the box there.

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Thanks @dyasny you have helped me more that once. Can you kindly provide a link to a Ubuntu signed driver if there is one. I found this from the link:link. There seems to be none for Ubuntu. I am trying to avoid using src to build and sign it. Will try out iozone and see how to use it. Again thanks! – taazaa Apr 8 '11 at 22:34
you can use these drivers with Ubuntu IMO, those are just images that contain windows binaries. – dyasny Apr 9 '11 at 9:03
I tried installing the drivers with - right click and install, That did not work. It says the Inf does not support this kind of install. Btw, do you know which folders to use from the ISO for network and storage? I am using F:\viostor\Wlh\amd64 for win 2008 64 bit storage and F:\NetKVM\Vista\amd64 for the Network drivers. – taazaa Apr 12 '11 at 2:02
how exactly did you "rightclick and install" ? the viostor driver should be picked while the windows VM is isntalled, otherwise, you shouldn't be able to see the virtio disk at all – dyasny Apr 12 '11 at 7:05
@dyasny, I was sure that would not work. The VM is booting using the HD and the bus in the xml says IDE. I somehow need to change it to a virtio disk, not sure how exactly. Do I change the boot sequence to use the cdrom first, then install the drivers? Do I add the driver iso as a second cdrom? Sorry I am new to this! Is there a step by step / readme on how to install this for a Win 2008 an existing VM? – taazaa Apr 12 '11 at 14:28

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