Re: call for testing: xen 4.1 packages

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Fri, Apr 01, 2011 at 04:02:54PM +0100, Jean-Yves Migeon wrote:
> On Fri, 1 Apr 2011 14:00:59 +0200, Manuel Bouyer
> <bouyer%antioche.eu.org@localhost> wrote:
> >On Fri, Apr 01, 2011 at 12:51:41PM +0100, Jean-Yves Migeon wrote:
> >>>I'm not sure this is the right way to do it; performance-wise.
> >>
> >>It's the only one reasonable for now, as they can be handled
> >>directly within a process. Otherwise, we have to make somekind of
> >>"vnd(4)" plugin, and implement sparse support (which is not as easy
> >>as it seems).
> >
> >I'm probably missing something here. Why do we need one process
> >(qemu-dm)
> >talking to another process to do I/O
> 
> The purpose is rather to support file formats that can offer block
> device functionality, without having to (re)write their support
> directly in kernel. AFAICT, vnd(4) does not support sparse files,
> and qcow/raw formats are sparse. The quickest way to expose those
> through a vnd(4) like interface is probably qemu-dm + pud(4).

but why do they need to be exposed as a vnd-like interface, if the
tool which will read them is already a userland process ? this
tool could read the filesystem image by itself, isn't it ?

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--