Hey Folks - We need your help. We were hoping, we could gain from your experience with implementing server virtualization. When should we be using Red Hat Virtualization, Citrix Virtualization, Xen Virtualization, Microsoft Virtualization, Oracle Virtualization and VMWare. I will be very interested in learning from your first hand experience. I will also like to know, under what situations is one virtualization preferred over the other. - Thanks for your help
Done in a sane fashion it can let you produce smaller, specialized machines. I used it to produce little web servers with their own IP address and https/ssl certificate.
If you try and put too many v-servers on one piece of hardware, you run into memory problems, i/o to disk problems and network throughput issues.
I also not by choice run linux v-servers running on a Microsoft host OS. This has been an unhappy experience. Windows gets busy once in a while and denies resources to my v-servers. With that set up I got all the problems I explained above plus the weaknesses of the Host OS, Windows 2003 server.
I use vmware on my laptop. I use it for configuration testing and such. I take a base system, test my patching methodology end to end and then restore the backup by closing the machine and copying a machine backup to the start location. Good tool, never load tested it.
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Red Hat, Oracle, and Citrix are all based on Xen. I've run Xen and VMWare systems.
VMWare Virtual Infrastructure (ESX) is the big name. If you have the money, I would recommend it over the others in most situations. There are plenty of third-party add-on products. Linux and Windows guests both work well. The admin console is the kind of pointy-clicky interface that people always think they need. The big down sides? A large VMWare environment costs a fortune, you may need to buy certified hardware for a real production environment, the admin console is slow and poorly designed, and unless you buy a product to do it you get almost no built-in reporting tools.
Xen works fine too, as long as you only need to run Linux guests and don't mind the relative lack of management tools. Xen with paravirtualized guests should usually be able to run better on small servers than VMWare will. There are various management tools for Xen, but I haven't found the ones I've looked at to be very impressive. I've done it all by hand, and the learning curve for that is a little steep. You can run Windows if you're on a new enough CPU, but everybody I've heard talk about it says it doesn't work very well yet.
VMWare Server is free, but it runs your VMs as processes inside a host OS just like an application. It works, but it's not nearly as fast as ESX. However, I think the VMWare Server console is actually better than the VirtualCenter/ESX client.
Just to clarify - Citrix bought Xen a while back and will be (maybe already has? I haven't been following them) releasing products based on it. Xen has no relation to the older Citrix environment that's already in widespread use, which is more like a terminal server for Windows apps but can offer some of the same benefits as virtualization.
