Re: [Qemu-devel] [RFC] block-trace Low Level Command Supporting Disk Introspection

[Richard W.M. Jones]

On Wed, May 22, 2013 at 03:38:33PM -0400, Wolfgang Richter wrote:
> On Wed, May 22, 2013 at 3:26 PM, Richard W.M. Jones <address@hidden>wrote:
> 
> > On Wed, May 22, 2013 at 02:32:37PM -0400, Wolfgang Richter wrote:
> > > On Wed, May 22, 2013 at 12:42 PM, Richard W.M. Jones <address@hidden
> > >wrote:
> > >
> > > > Run up to two extra guestfish instances, with the same result.  The
> > > > fourth guestfish instance hangs at the 'run' command until one of the
> > > > first three is told to exit.
> > >
> > >
> > > And your interested on being notified when a snapshot is "safe" to read
> > > from?
> > > Or is it valuable to try reading immediately?
> >
> > I'm not sure I understand the question.
> >
> > I assumed (maybe wrongly) that if we had an NBD address (ie. Unix
> > socket or IP:port) then we'd just connect to that and go.
> 
> 
> I meant if there was interest in reading from a disk that isn't fully
> synchronized
> (yet) to the original disk (it might have old blocks).  Or would you only
> want to
> connect once a (complete) snapshot is available (synchronized completely to
> some point-in.

IIUC a disk which wasn't fully synchronized wouldn't necessarily be
interpretable by libguestfs, so I guess we would need the complete
snapshot.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org