[Sheepdog] cloning image fails

[MORITA Kazutaka]

On 2010/01/08 7:09, Piavlo wrote:
>  Hi,
> 
> Snapshot works but cloning fails with current master branch:
> 
> fire-srv4 ~ # qemu-img snapshot -c name sheepdog:zopa1
> sd_claim 1492: zopa1
> sd_release 1533: zopa1
> sd_close 1478: zopa1
> fire-srv4 ~ # qemu-img create -b sheepdog:zopa1 -f sheepdog zopa2
> sd_close 1478: zopa2
> Formatting 'zopa2', fmt=sheepdog size=5368709120 backing_file='zopa2'
> qemu-img: Error while formatting
> fire-srv4 ~ #  shepherd info -t vdi
>    40000 : zopa1  5120 MB (allocated: 4068 MB, shared: 0 MB), 2010-01-07
> 23:14:25, tag:        0, not current
>    80000 : zopa1  5120 MB (allocated: 0 MB, shared: 4068 MB), 2010-01-07
> 23:30:01, tag: 4b465259, current
> fire-srv4 ~ #                                      

The usage to create a clone image is as follows:

  qemu-img create -b sheepdog:[base vdiname]:[tag id] -f sheepdog [new vdiname]

Please note that you can create a clone image only from a snapshot vdi (read only image).
When creating clone from a snapshot image, you need to specify the vdi tag id
because base vdi may have more than one snapshots and qemu-image need to know
which image you want to create clone from.

In your case,

$ qemu-img create -b sheepdog:zopa1:0 -f sheepdog zopa2

will work, probably.

> Also I am able to boot the snapshot VM and login into it, but i gets
> stuck after a short time as well as all shepherd
> commands on all nodes. After killing the VM and restarting all the
> sheepdogs - they can communicate again with each other
> and see all the previously  existing images correctly.

It seems to be a bug of sheepdog. I'll fix it.

>  Is it possible to boot concurrently both the image and it's snapshot?
> and in which mode ie. read/write?

No, it isn't. The image will be locked if you start one of them.
Though snapshot images are read-only, you can boot from a snapshot image as
writable mode because sheepdog automatically generates a new vdi
when VM writes data to the snapshot image.

> Same question for an image and it's clone.

Yes, you can.

Regards,

Kazutaka Morita