Live Cross-Cloud Migrations With Aeolus and Snap

[Richard W.M. Jones]

On Fri, Nov 04, 2011 at 09:59:39AM +0000, Richard W.M. Jones wrote:
> On Thu, Nov 03, 2011 at 09:17:55PM -0400, Mo Morsi wrote:
> > See the following step-by-step guide (complete w/ screenshots ) [1]
> > that I threw together on how to use Aeolus and Snap [2] to migrate a
> > running instance between two separate cloud providers with no
> > downtime (demonstrated is EC2 / rackspace but this will work to/from
> > RHEV-M or any other cloud provider supported by aeolus/deltacloud
> > [3])
> > 
> >   -Mo
> > 
> > [1] http://mo.morsi.org/blog/node/347
> > 
> > [2] https://github.com/movitto/snap
> > 
> > [3] http://incubator.apache.org/deltacloud/drivers.html#h2
> 
> You mention in the blog posting that you can restore to another Linux
> distro.  But would this really work?  How about if there were two
> different Apache versions, each with a slightly different
> configuration syntax?  Or more plausibly, two different PostgreSQL
> versions (PG's on-disk format is not compatible across some version
> changes).

Some follow-up questions ..

How large is the snap metadata, ie. the stuff that you copy between
the machines?  How large would it be given, say, a typical
database-backed webserver installation where you might have lots of
static contents and some database tables?

Is the metadata in an ad-hoc format and how hard would it be to turn
it into a standard format (probably one that we would standardize
ourselves)?  Can it be useful in other contexts -- eg.  could a system
administrator look at the output in order to get a definitive list of
the changes made to the machine?  Could it be useful for auditing?
Could the format be diffed?

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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