[fedora-virt] virtio block driver performance versus ide

[Pasi Kärkkäinen]

On Thu, Oct 15, 2009 at 08:45:52PM -0400, Paul Lambert wrote:
>    I will second this performance observation.  After the latest round of
>    pathces, I too found that my Windows XP VM was performing much faster than
>    before and consuming much less cpu time.  I then observed that my Fe-11 VM
>    was performing considerably slower.  Sure enough, I have checked my hda
>    for each VM and the Windows was using native IDE and FE-11 was using
>    virtio.  I have now changed my FE-11 hda to IDE.  Seems to exhibit much
>    more pep!  So much for paravirtualization.
> 

It sounds like the kvm virtio drivers are not working like they should.
possible a bug in the drivers..

At least Xen PV drivers are faster than emulated IDE, and use less CPU.

-- Pasi

>    Paul
> 
>    On Thu, Oct 15, 2009 at 3:50 PM, Dale Bewley <[1]dlbewley at lib.ucdavis.edu>
>    wrote:
> 
>      I assumed the virtio block driver to be faster for a kvm guest than ide,
>      but I'm seeing quite the opposite. Is this expected?
> 
>      I normally create guests with a wrapper script around virt-install which
>      creates guests configured to use IDE disks:
> 
>      f11-db1.xml-    <emulator>/usr/bin/qemu-kvm</emulator>
>      f11-db1.xml:    <disk type='file' device='disk'>
>      f11-db1.xml-      <source file='/var/lib/libvirt/images//f11-db1.img'/>
>      f11-db1.xml-      <target dev='hda' bus='ide'/>
>      f11-db1.xml:    </disk>
> 
>      I am currently creating a guest with the virt-manager wizard which
>      apparently uses virtio by default:
> 
>      f11-archivist.xml-    <emulator>/usr/bin/qemu-kvm</emulator>
>      f11-archivist.xml:    <disk type='file' device='disk'>
>      f11-archivist.xml-      <source
>      file='/var/lib/libvirt/images//f11-archivist.img'/>
>      f11-archivist.xml-      <target dev='vda' bus='virtio'/>
>      f11-archivist.xml:    </disk>
> 
>      The filesystem formatting and installation are going very very slowly.
> 
>      Host is 2.6.29.6-213.fc11.x86_64 4x quad core. Guests are also fc11
>      x86_64.
> 
>      BTW, I've updated to virt-manager-0.7.0-7, libvirt-0.6.2-18,
>      qemu-kvm-0.10.6-6, and kernel-2.6.30.8-64 just before creating this
>      guest but have not restarted libvirtd or rebooted the host.
>      --
>      Dale Bewley - Unix Administrator - Shields Library - UC Davis
>      GPG: 0xB098A0F3 0D5A 9AEB 43F4 F84C 7EFD  1753 064D 2583 B098 A0F3
> 
>      _______________________________________________
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> 
> References
> 
>    Visible links
>    1. mailto:dlbewley at lib.ucdavis.edu
>    2. mailto:Fedora-virt at redhat.com
>    3. https://www.redhat.com/mailman/listinfo/fedora-virt

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