[sheepdog] reply: execute the snapshot vm became read-only

[Liu Yuan]

On Fri, Aug 09, 2013 at 04:33:36PM +0800, Liu Yuan wrote:
> On Fri, Aug 09, 2013 at 08:19:22AM +0000, 周鹏 wrote:
> > 
> > On Fri, Aug 09, 2013 at 03:03:13AM +0000, zhoupeng wrote:
> > > hello,i test snapshot of sheepdog version 0.6 stable.
> > > first,i start the sheep with one node:
> > >
> > > #!/bin/bash
> > > sheep /home/cloud -u -g -d 64 -z 0 -D -c local
> > > for i in {0..0}
> > > do
> > > sheep /home/${i} -u -D -d -c local -p $((7001 + $i))
> > > done
> > >
> > > then i use libvirt to start the vdi, by using vnc to login the vdi;
> > > i create a file and write sth, everything is ok;
> > >
> > > but after i execute the snapshot:
> > > qemu-img snapshot -c sheepdog:centos6 sheepdog:centos6
> > 
> > Your qemu might be too old. Try latest QEMU at git://git.qemu.org/qemu.git
> > 
> > thanks much.i have update qemu to the latest. Excute snapshot is ok now, but 
> > when the vm is running, perform the following steps:
> > 1.  write some data to a file
> > 2.  sync
> > 3.  create a snapshot
> > 4.  delete the file.
> > 5.  shutdown the vm rollbak to the snapId(collie vdi rollback centsos6-test -s 11)
> > 6.  enter the vm and the file came back
> > 
> > but if not shutdown the vm, excute above steps, the file will not be restored.it means that sheepdog
> > dose not support hot snapshot. am i right?
> 
> Sheepdog fully support live snapshot both for memory state (savevm) and disk only
> state(qemu-img snapshot or collie snapshot).

Typo. savevm both save memory state and disk state and sheepdog will store these
states in the cluster for you (This means both disk and memory state of snapshots
are replicated in sheepdog)

Thanks
Yuan