Re: [Qemu-devel] [PATCH 0/5] VMWare PVSCSI paravirtual device implementation

[Daniel P. Berrange]

On Thu, Mar 15, 2012 at 11:47:29AM +0000, Stefan Hajnoczi wrote:
> On Thu, Mar 15, 2012 at 9:02 AM, Dmitry Fleytman
> <address@hidden> wrote:
> > Below is the implementation of VMWare PVSCSI device and
> > command line parameters to configure vendor name and product name
> > for SCSI storage are implemented.
> > Latter is needed to make PVSCSI storage devices look exactly as
> > on VMWare hypervisors.
> >
> > With this and VMWARE3 patches V2V migration problem for VMWare
> > images should be solved relatively easy.
> 
> What is the V2V strategy?
> 
> Supporting these devices is fine if we have a way to convert guests to
> use virtio.  But if the plan is to keep the guests on VMware pv
> devices, then that will split the development effort on support and
> optimizing I/O devices.  All the performance work going into
> virtio-net (vhost-net), virtio-blk, and possibly virtio-scsi isn't
> easy to duplicate for VMware pv devices.  Also, we cannot extend
> VMware devices easily while retaining compatibility.
> 
> I'm for supporting these devices, but we really need another step to
> move migrated guests onto virtio - otherwise users will be
> disappointed with KVM's support/performance.  Can you explain a bit
> how you want these devices to be used?

FWIW, there is a v2v tool that is able to update guest images to
port them from VMware to KVM, which covers changing the drivers,
but also a bunch of other things

  http://libguestfs.org/virt-v2v/


I can still see value in natively supporting the VMWare PV devices
though, since it could facilitate people who just want to try out
pre-built appliance images which were designed only to use those
devices.

Daniel
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