Re: [Qemu-devel] [PATCH v3 4/8] replay: save/load initial state

["Pavel Dovgalyuk" <dovgaluk@ispras.ru>]

> From: Paolo Bonzini [mailto:pbonzini@redhat.com]
> On 20/09/2016 15:37, Pavel Dovgalyuk wrote:
> >> c) no rrsnapshot implies -snapshot:
> >>    without overlay:
> >>       -drive file=disk.raw,if=none,id=img-direct
> >>       -drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay
> >>
> >>    with overlay:
> >>      -drive file=foo.qcow2,if=none,id=img-direct
> >>      -drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay
> >>      -icount ...,rrsnapshot=snapname
> >
> > But how record will create this overlay?
> > This method requires creating overlay manually, because backing file is
> > not specified at all.
> 
> You create it manually, or you just use a .qcow2 file to begin with for
> your image.  Then:
> 
> 1) if you specify no snapshot, a temporary .qcow2 file is created on top
> so data is not destroyed
> 
> 2) if you specify a snapshot, that snapshot is preserved (so you don't
> lose the base state even though the file changes)

Now I see.
This seems ok, but:
 - this approach adds some garbage to original disk image
 - won't work with raw images

Pavel Dovgalyuk