Re: [Qemu-devel] Re: Strategic decision: COW format

[Anthony Liguori]

On 02/23/2011 09:37 AM, Avi Kivity wrote:
> On 02/23/2011 05:31 PM, Anthony Liguori wrote:
> > > > what about snapshots?  Are we okay having a feature in a prominent 
> > > > format that isn't going to meet user's expectations?
> > > >
> > > > Is there any hope that an image with 1000, 1000, or 10000 snapshots 
> > > > is going to have even reasonable performance in qcow2?
> > >
> > > Are thousands of snapshots for a single image a reasonable user 
> > > expectation?  What's the use case?
> >
> >
> > Checkpointing.  It was the original use-case that led to qcow2 being 
> > invented.
>
> I still don't see.  What would you do with thousands of checkpoints?

Er, hit send to quickly.

HPC is a big space where checkpointing is actually useful.  An HPC 
workload may take weeks to run to completion.  If something fails during 
the run, it's a huge waste of time.  However, if you do regularl 
checkpointing, a failure may only lose a few minutes of work instead of 
the entire weeks worth of work.

Regards,

Anthony Liguori