Re: [Xen-users] Xen clustering

[Tom Brown <xensource.com@xxxxxxxxxxxxxxxxxxx>]

On Wed, 31 Oct 2007, Nico Kadel-Garcia wrote:

> shacky wrote:
> >  Hi.
> >
> >  I'm writing to the mailing list to know if Xen is what I'm looking for.
> >  I need a failover cluster with two completely and automatically
> >  replicated and redundanced servers running Windows Server 2003
> >  Standard.
> >  Could Xen make this?
> >  Where I can found some information about making this configuration with
> >  Xen?
> >
> >  Thank you very much for your help!
> >
> >  Bye.
> Not..... exactly. You can keep multiple operating systems on a single 
> server: you can migrate them from a common network storage to run on one 
> server or another. But failover where one server's operating system 
> fails or is disabled, and another takes over the function, is a much 
> more interesting thing to do. To do complete OS failover, every physical 
> component must be mirrored and matched and the connections duplicated
what? Even if "every component must be matched", that would be a GREAT 
reason to use XEN, as all the components are virtual, so of course they 
match.
.. And using XEN underneath a proprietory O/S allows you to do things like 
replicate the filesystem via DRBD to another node... and/or make backups 
via snapshots, etc...
So, while the question is incomplete, and XEN isn't going to do the job by 
itself, it is a very usefull tool in getting the job done... as putting 
the proprietary OS inside a virtual machine gives you a degree of control 
you might not be able to get on physical hardware. I've got a couple of 
physical windows servers that I _wish_ were running inside virtual 
machines.
That said, while I do use DRBD in production, I have not configured 
heartbeat to configure automated failover of services... nor do I make 
much use of windows.
-Tom

> with failover redundancy, and that gets fascinating to support. It's 
> also amazingly expensive, much more than the cost of a small set of 
> duplicate servers.
Nico, I like some of your answers... and some of them leave my mouth 
hanging open. You don't leave yourself much wiggle room, it would be 
really easy for some newbie to think they were "the definitive" answers.
> If you have specific services running on those servers, you might be able to 
> gracefully implement them in normal master/slave or master/master failover 
> modes.
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