[Linux-HA] HA of virtual machiens

[Dejan Muhamedagic]

Hi,

On Fri, Feb 01, 2008 at 11:44:16AM +0100, Michael Schwartzkopff wrote:
> Hi,
> 
> we want to offer services on 4 servers. These services should be high 
> available. All services will have very low usage.
> 
> 1) The first plan was to use 8 servers and create 4 HA-clusters. But 8 servers 
> doing very little is waste of money. So the next plan was:
> 
> 2) Use 5 servers, build one big cluster and distribute the services in such a 
> way, that not two services run on the same machine. One spare is left with 
> this architecture.
> 
> 3) Next plan: Use only two physical servers, create 8 virtual servers, build 
> one cluster on the physical machines and have heartbeat look for the virtual 
> machines. But the problem with this setup is that monitoring of the virtual 
> machines does not look, if the applications on these virtual machines do 
> really run.

There are hooks in the Xen RA for service monitoring. I've never
used that, but it should work.

> 4) Next plan: Setup as before, 2 cluster between the two physical machines, 4 
> clusters between the 8 virtual machines. Monitoring on the cluster of the 
> physical machines looks for the health of the virtual machines and monitoring 
> in the virtual clusters look for the health of the applications.
> 
> My question: What is really the best solution?
> Isn't solution 4) far too complex?

I'd say yes.

> What is your oppinion. Thanks for any answer.

Options 2 or 3. Note that you'll probably have higher maintenance
costs with option 3 as well as more complex configuration. And
lower hardware cost. It's really a matter of preference. I'd
probably go with option 2) and reduce the number of nodes if
possible.

Thanks,

Dejan

> Sincerely,
> -- 
> Dr. Michael Schwartzkopff
> MultiNET Services GmbH
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