[Sheepdog] The 's' flag

[Brian Candler]

On Mon, Aug 22, 2011 at 03:18:07PM +0900, MORITA Kazutaka wrote:
> > However, in my tests the 's' flag is applied to everything except the last
> > snapshot:
> > 
> > brian at x100:~$ collie vdi list
> >   name        id    size    used  shared    creation time   vdi id
> > ------------------------------------------------------------------
> > s Test         1  2.0 GB  472 MB  0.0 MB 2011-08-16 21:00   ec9f05
> > s Test         2  2.0 GB  0.0 MB  472 MB 2011-08-16 22:44   ec9f06
> > s Test         3  2.0 GB   48 MB  424 MB 2011-08-16 22:46   ec9f07
> > s Test         4  2.0 GB   56 MB  416 MB 2011-08-16 22:46   ec9f08
> > s Test         5  2.0 GB   44 MB  428 MB 2011-08-16 23:04   ec9f09
> >   Test         6  2.0 GB   48 MB  424 MB 2011-08-16 23:05   ec9f0a
> > 
> > This suggest to me that 's' means 'shared'?
> 
> No, the 's' flag means a snapshot.  I think you ran
> "qemu-img snapshot -c tag sheepdog:Test" five times, no?

Not exactly. I can't remember the exact sequence of what I did to get to
that point but it includes the following:

* I created a vdi and booted with an Ubuntu cd-rom image, and did the
  install. This gave me image id 1 (size 2.0GB, used 472MB)

* I created at least one snapshot from it

* I tried booting the original image and the snapshot. As far as I can see,
  booting the snapshot caused a new snapshot to be created.

* I tried booting the original image (id 1) more than once. It allowed me
  to do so; both VMs had writable access to the same underlying block
  device (e.g. if I overwrite an unused file in /etc from one VM with a
  test message, and then cat it from the other, I can see the data I wrote).

This last thing seems like a bug, but I haven't reported it yet because
I need to confirm the exact steps to reproduce.

Regards,

Brian.