Re: [Qemu-devel] tcmu-runner and QEMU

[Benoît Canet]

The Saturday 30 Aug 2014 à 15:46:41 (+0100), Richard W.M. Jones wrote :
> For the benefit of those who have absolutely no idea what you're
> talking about, could you write a simpler summary of what you're trying
> to do?
> 
> Rich.

Hello,

Most cloud providers sell virtualized instances either using Xen or KVM.

However another trend is to provide bare metal instances for people who want 
the highest
CPU and network performance possible.(typicaly people doing computation with 
MPI)

So a cloud end user would need to be able to instanciate a virtual machine use 
it for a while
then stop the virtual machine, change the hardware type to bare metal and 
restart the instance
while keeping using the same boot volume.

QEMU will keep a virtual machine data stored in one of it's numerous storage 
backend format
like QCOW2 or QED.

If the cloud provider want to be able to boot QCOW2 or QED images on bare metal 
machines
he will need to export QCOW2 or QED images on the network.

So far only qemu-nbd allows to do this and it is neither well performing nor 
really convenient
to boot on a bare metal machine.

So summarize I am looking for a way to export QCOW2 or QED image as an ISCSI or 
FCOE
targets while keeping all the goodies these format provides (taking snapshots 
for backup,
streaming, mirroring).

Reusing LIO code would help tremendously to simplify this task.

Best regards

Benoît

> 
> -- 
> Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> libguestfs lets you edit virtual machines.  Supports shell scripting,
> bindings from many languages.  http://libguestfs.org
>