I will look in to XCP.. but my guess is that they use their pv drivers to
communicate via xenstore..etc. I am looking for something that would work with
vanilla open source xen. (well non XCP :) )
But my plan is same as I described in skeleton and organization very similar to
yours. but to have something that works with ssh/wmi. This way scripts etc can
be centrally managed.
What I was looking for was
-- For xen is there a flush command for PV and HVM vms. (hypervisor level)
-- Is sync sufficient as a starting point at OS level.
-- Any repository of application specific scripts. (Mysql,oracle..etc)
-- And anything to control cpu/io consumption of the backup process. (Probably
start with cstream / nice)
-nb
--- On Thu, 1/14/10, Pasi Kärkkäinen <pasik@xxxxxx> wrote:
> From: Pasi Kärkkäinen <pasik@xxxxxx>
> Subject: Re: [Xen-users] Fw: coordinating VM snapshot with LVM snapshot.
> To: "J Nb" <j_nwb@xxxxxxxxx>
> Cc: "xen-users" <xen-users@xxxxxxxxxxxxxxxxxxx>
> Date: Thursday, January 14, 2010, 9:15 AM
> On Wed, Jan 13, 2010 at 09:11:47AM
> +0200, Pasi Kärkkäinen wrote:
> > On Tue, Jan 12, 2010 at 05:44:18PM -0800, J Nb wrote:
> > > Anyone ?
> > >
> >
> > Now that XenServer is opensourced as XCP (Xen Cloud
> Platform), you could
> > take a look at the source..
> >
> > I believe XenServer supports Windows VSS coordination
> for snapshots.
> > "xe vm-snapshot-with-quiesce"
> >
>
> Did you get anywhere with this?
>
> For a long time I've been thinking of writing some kind of
>
> "VSS" library/daemon for Linux.. similar to Microsoft
> Windows
> Volume Snapshot Services.
>
> It could (and should) be called something different than
> VSS,
> but I'll just use that name for now..
>
> The interface/usage could be something like:
>
> 1. backup begins
> 2. execute in the guest: "vss_control
> pre-snapshot xvda"
> 3. take snapshot of the lvm volume
> having guest disk xvda
> 4. execute in the guest: "vss_control
> post-snapshot xvda"
> 5. do the actual backup from the lvm
> snapshot
> 6. backup ends
>
> This would have minimal downtime for the applications
> running in the guest.
>
> pre-snapshot action would go through all the application
> specific pre-scripts,
> execute them, preparing the applications for taking the
> snapshot, and then
> it would flush the filesystem, kernel and disk caches as
> needed to prepare for
> a consistent snapshot.
>
> Preparing the application for taking the snapshot might
> mean something
> like placing locks to database tables preventing disk
> writes from happening,
> or shutting down the application, or whatever the specific
> application requires.
>
> post-snapshot action would again go through and execute all
> the application specific
> post-scripts releasing the applications back to normal
> running state.
>
> The application specific pre/post scripts could be stored
> like this:
>
>
> /etc/vss/scripts/xvda/001-mysql.pre
> /etc/vss/scripts/xvda/001-mysql.post
>
> /etc/vss/scripts/xvda/002-pgsql.pre
> /etc/vss/scripts/xvda/002-pgsql.post
>
>
> /etc/vss/scripts/xvda/003-my_custom_app.pre
>
> /etc/vss/scripts/xvda/003-my_custom_app.post
>
> Or you could have "scripts/xvda2/*" if you have lvm volumes
> directly as
> partitions to the guest. You get the idea.
>
> Then the next step would be to create a daemon ("vssd")
> that listens for
> requests from the network, and/or possibly from Xen dom0
> through the hypervisor.
>
> Or then the backup server might issue those pre-snapshot
> and post-snapshot
> commands through ssh.. many options how to implement it.
>
> Does this make any sense? Comments?
>
> -- Pasi
>
> >
> > >
> > > --- On Sun, 1/3/10, J Nb <j_nwb@xxxxxxxxx>
> wrote:
> > >
> > > > From: J Nb <j_nwb@xxxxxxxxx>
> > > > Subject: coordinating VM snapshot with LVM
> snapshot.
> > > > To: xen-devel@xxxxxxxxxxxxxxxxxxx
> > > > Date: Sunday, January 3, 2010, 6:17 PM
> > > > Hi
> > > > How to co-ordinate VM snapshots and
> disk
> > > > snapshots ? Here is a sequence I am thinking
> of
> > > > automating...
> > > >
> > > > 1.Tell VM to sync (say via ssh or some
> special
> > > > agent)
> > > > * This will do "sync" and any
> > > > application specific hook to make it
> quiescent.
> > > >
> > > > 2. Tell VM/Hypervisor to flush all disk
> buferes
> > > > ? (HOW ??? )
> > > > * Anything at this level?
> > > >
> > > > 3. Pause the VM
> > > >
> > > > 4. xm save -c (To save the VMs state in
> to
> > > > checkpoint file.)
> > > > (This may take more time !)
> > > >
> > > > 5. Take LVM snapshot for each disk.
> > > >
> > > > 6. Unpause the VM
> > > >
> > > > 7. Application level resume if any.
> > > >
> > > > 7. Use the snapshot to copy each disks
> ?!!!! (either
> > > > dd or mount followed by cp/rsync) (This
> can be big!
> > > > Any optimization suggestions )
> > > >
> > > > 8. discard snapshot.
> > > >
> > > >
> > > > Would the above sequence work ?
> > > >
> > > > Any suggestions on individual steps ?
> > > >
> > > > Anything specific for PV and HVM virtual
> machines?
> > > >
> > > > Is there a backdoor to qemu-dm console ?
> > > >
> > > > Does anyone know how similar functionality
> is implemented
> > > > in XenServer product or Virtual Iron or
> anyone else?
> > > >
> > > > -nb
> > > >
> > > >
> > > >
> > > >
> > >
>
>
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