Re: [et-mgmt-tools] Re: [libvirt] RE: [Qemu-devel] [ANNOUNCE] virt-mem tools version 0.2.8 released

Daniel P. Berrange
2008-08-12T10:31:05Z

On Tue, Aug 12, 2008 at 10:25:34PM +1200, james wrote:
>
> On 11/08/2008, at 8:42 PM, Daniel P. Berrange wrote:
> >Configuring SCSI disks with VMs in libvirt is no different to
> >configuring
> >any other kind of block based storage. The general description is
> >here:
> >
> > http://libvirt.org/formatdomain.html#elementsDisks
> >
> >Specifically though you'd want a disk section looking like
> >
> > <disk type='block'>
> >
> > <target dev='sda' bus='scsi'/>
> > </disk>
> >
> >NB, there is no restriction on mapping to the target bus -ie a SCSI
> >disk in
> >the host can be mapped to a IDE disk in the guest, and vica-verca.
> >Also
> >note that the 'dev' attribute on the target isn't a guarenteed
> >device name
> >in the guest - it is merely used for ordering of devices when
> >spawning QEMU.
> >
> >Now, the main fun you'll have is actually outside of libvirt -
> >namely that
> >on Linux SCSI disk names are not guarenteed stable across reboots. So
> >rather than using /dev/sdf1 you may want to consider one of the udev
> >created
> >stable paths under the directories /dev/disk/by-{id,path,uuid}, or
> >if you are
> >using a multipath enabled SAN, then a name under /dev/multipath/XXXX
> >
> >Regards,
> >Daniel
>
> To be clear I have not tried to use block devices but 5 image files as
> I am experimenting. I have tried to create VMs using raw image files
> under libvirt via the nice Virtual Machine Manager 0.5.3 and through
> hand crafted xml files. Neither method will register the images as
> scsi disks, it fails with an error. Getting the same disk images to be
> regarded as scsi disks via the kvm command line is fine or if I fall
> back to ide and limit. The ide test proves that the rest of the xml
> file is correct.
>
> Trying to define a domain using virsh using a disk section defined as:
>
> <disk type='file' device='disk'>
>
> <target dev='sda' bus='scsi'/>
> </disk>
>
> fails with this error:
> libvir: QEMU error : Invalid harddisk device name: sda

Oh, that means the version of libvirt you are using is too old - it
predates us adding support for the -drive argument, which is required
in order to use SCSI disks. THis was added in libvirt 0.4.3

Regards,
Daniel
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