Re: [Qemu-devel] Re: NBD server for QEMU images

[Mark Williamson <mark.williamson@cl.cam.ac.uk>]

> > > It's mostly intended to be used for accessing the files inside QEMU
> > > disk images locally, without having to launch a virtual machine and
> > > accessing then from there.
> >
> > mount -o loop does this.
>
> How is everybody missing the point? :-)  mount -o loop doesn't mount
> qcow images.

Using dm-userspace (a device mapper with mappings generated by a userspace 
daemon instead of a kernel module) I believe it is possible to mount all 
kinds of weird and wonderful things - including things like qcow.

The patches for dm-userspace are floating around, I think on the device mapper 
and Xen developer's mailing lists.

Of course, this is a Linux-specific solution so an NBD server is probably 
still useful (can other OSes mount NBD?  I assume so...?).

In principle, you could use the NDB server to host storage for physical 
machines too, right?  For instance you could opt for a fairly "thin" setup 
where all user disks are stored separately in qcow format to save space.  
This might be nice for some users of centralised storage systems...

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!