Re: virtual drive performance

Gianluca Cecchi <gianluca.cecchi@xxxxxxxxx> · Tue, 20 Jun 2017 16:24:32 +0200

On Tue, Jun 20, 2017 at 3:38 PM, Dominik Psenner <dpsenner@xxxxxxxxx> wrote:

    to the following:

    <disk type='file' device='disk'>

        <driver name='qemu' type='qcow2' cache='none'/>

        <source
file='/var/data/virtuals/machines/windows-server-2016-x64/image.qcow2'/>

        <backingStore/>

        <target dev='hda' bus='scsi'/>

        <address type='drive' controller='0' bus='0' target='0'
      unit='0'/>

      </disk>
    Do you see any gotchas in this configuration that could prevent
      the virtualized guest to power on and boot up?

When I configure like this, from a linux guest point of view I get this Symbios Logic SCSI Controller:
00:08.0 SCSI storage controller: LSI Logic / Symbios Logic 53c895a

But htis is true only if you add the SCSI controller too, not only the disk definition.
In my case

    <controller type='scsi' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
    </controller>

Note the slot='0x08' that is reflected into the first field of lspci inside my linux guest.
So between your controllers you have to add the SCSI one

In my case (Fedora 25 with virt-manager-1.4.1-2.fc25.noarch, qemu-kvm-2.7.1-6.fc25.x86_64, libvirt-2.2.1-2.fc25.x86_64) with "Disk bus" set as SCSI in virt-manager, the xml defintiion for the guest is automatically updated with the controller if not existent yet.
And the disk definition sections is like this:

    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source file='/var/lib/libvirt/images/slaxsmall.qcow2'/>
      <target dev='sda' bus='scsi'/>
      <boot order='1'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>

So I think you should set dev='sda' and not 'hda' in your xml for it

I don't kknow if w2016 contains the symbios logic drivers already installed, so that a "simple" reboot could imply an automatic reconfiguration of the guest....
Note also that in Windows when the hw configuration is considered heavily changed, you could be asked to register again (I don't think that the IDE --> SCSI should imply it...)

Gianluca

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