The state of XEN vs KVM for inhouse virtual server farm like live farm

so we have a life server Farm, conventional stuff not virtualized. This is to stay that way for the time beeing. The servers we are talking about are: Loadbalancer, DB master, DB Slaves (2x), Webservers (2x), CMS server. All in all 7 servers per farm.

We want to have one to many rather exact "copies" of the life structure for inhouse purposes.

• Testing/Staging: to find bugs before live that might slip through if we do not use the same software-configuration
• Debugging/Benchmarking: Same like testing but with additional tools. debug flags and isolated from Tetsing/Staging to not interfeer with QA. Intended to get a deeper insight into how things are on our live-sys开发者_开发知识库tems
• Development/Experimental: Changing System Components, Software-Versions, Libraries and Configuration to improve performance, developer effectivness, future-proofing our systems etc.

All in all 3 virtual "farms" a 7 virtual servers each, neatly isolated.

Now I know this can be achieved with many different flavors of virtualization. The Questions is, what is the best? VMware not beeing open source is nothing we would like to use on a strategic point of view. Looking at XEN and KVM, the two biggest players in open source virtualization I would love to hear some advise on what/how to select. The Web seems undecided.

Additional Info:

• "life time" of the server hardware that we purchase will be 2-3 years
• There is the possibility that we might migrate systems into cloud-environments later, if that is a factor to consider in the selection of the virtualization-technology
• Isolation of Server-Farms/Servers in High-Load scenarios is important. QA should not suffer when someone wrecks havoc in the experimental farm
• Efficent ressource usage is of course appreciated (memory overcommitment/shared pages? Automaticly Shared objects on hard-drive like the linux-vserver hashify?)
• Regular maintenance requierements and easy of management

I know things are in the flow but I would appreciate if you would tell me your opinion on what to choose right now seeing we want to live with the technique for at least 3 years, build up and reuse know-how. Also maybe in the end we can all realize that neither one, XEN or KVM is deciding the battle but other factors. Enlightenment in that regards is even more valuable to us right now.

p.s.: and lets not flame :D

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I can't help with your query, but maybe it would help others if you told us what OS you need to run on each of the 7 servers, and at least approximately what resource requirements those servers must respond to (RAM, mass storage, CPU, network).