Xen users - Nov 2007 - Re: XEN : Is there any way for sharing base virtual image.?

Hi Christian ,

Its good to know the concept given by you.I found one more thing to work the
same like stuf.. even you will feel nice about it.

UnionFS based snapshotting Or having a Read only based virtual machines.

Just give a try and give the feedback. Since i found this concept
interesting.

http://flaviostechnotalk.com/wordpress/index.php/2005/06/28/filesystem-snapshots-with-unionfs/


Regards
Arun Sharma

On 11/2/07, Christian Horn <chorn@fluxcoil.net>
wrote:
>
> On Fri, Nov 02, 2007 at 07:01:35PM +0530, Arun Sharma wrote:
> >
> > So can you give me the steps by step doc on how to implemnent the same
> you
> > are talking about. So that i can have a try.
>
> The basic steps using usual lvm2 are:
>
> - create a pv, i.e. if /dev/sdc is a disc you want to use:
>         pvcreate /dev/sdc
>
> - create a volumegroup containing the created pv:
>         vgcreate vg_xen /dev/sdc
>
> - create your master-volme:
>         lvcreate -L 7G -n lv_master vg_xen
>
> - create the master-domU: create a xen-domU using
>   phy:/dev/vg_xen/lv_master as disc and install your OS
>
> - shutdown the master-domU
>
> - create the first snapshot:
>         lvcreate -s -L 2G -n lv_snap01 /dev/vg_xen/lv_master
>   The above leaves 2G storage for changes that the slave-domU can
>   make in the snapshot.
>
> - create the first slave-domU: create a xen-configfile mostly
>   similiar to the master-domU config, change domU name, and
>   use phy:/dev/vg_xen/lv_snap01 as disc
>
>
>
> Christian
>


-- 


Regards
Arun Sharma
0-934-829-3810


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On Sat, Nov 03, 2007 at 02:50:10PM +0530, Arun Sharma
wrote:
> 
> Its good to know the concept given by you.I found one more thing to work
the
> same like stuf.. even you will feel nice about it.
> 
> UnionFS based snapshotting Or having a Read only based virtual machines.
> 
> Just give a try and give the feedback. Since i found this concept
> interesting.
> 
>
http://flaviostechnotalk.com/wordpress/index.php/2005/06/28/filesystem-snapshots-with-unionfs/
Reading this it could actually be interesting if one gets it running on
a cluster-filesystem that is accessed by the dom0 and domUs.
More complicated than lvm-snapshots but:

- should work with more than one dom0 accessing the cluster-fs, so
migration should work (clvm and evms/heartbeat dont allow snapshots
in that mode as far as i know)
- and one can make more than one snapshot, with lvm2 i wasnt able
to create a snapshot of a snapshot, which would be nice for doing 
backups of a domU that runs from the first snapshot
- and using unionfs should safe space, instead of dedicating an amount
of space to a lvm-snapshot and increasing this if needed unionfs just
uses space from the underlying filesystem

Sounds really nice ]-)
Please report if you tried.


Christian

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