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When we started we bought these boards http://www.supermicro.com/products/motherboard/QPI/5500/X8DT... and at first we outfitted them with one low end CPU and small amount of ram 6G as those were our needs and that's what we could afford at the time. 2 years ago we upgraded those machines with dual 5560 cpus, and 48Gram for not very much money, and in fact they run our production DBs right now. They still are very competitive if you stack them up to current e5 models. We added more servers last 2 years and they have been E3-1240 V2 based single cpu, 32G ram. You can't beat the price/performance there.
So in 4 years we still have not obsoleted much but some older ram and base cpus. KVM is really easy to setup. Install the package on your linux distro, start up virt-manager if you want gui, "start" new machine and install whatever you want from any cd image you have.
Of course once you wrap your head around it you'll want to do it with cli tools and custom automate it. But basic virt-manager might take you a long way.
Once you have multiple machines and you want to migrate between hosts you'll have to setup a shared storage. That can be as easy as an nfs share/mount. We started with just 1 ssd for that, but then built a dedicated box with many intel ssds on hardware raid 10. Never had an issue.
But shared storage/live migration is not always needed and can add more risk. If you engineer it that all your hosts are independent and you have redundant services for everything, then you dont need to live migrate. If you need to free up that host, just turn it off, as you have redundant services running on other hosts. In fact on our Dev systems we run KVM on our osx laptops nested in a vmware vm. ( vmware can nest like this passing hardware flags to the guest host ) So on osx you run vmware, which runs a linux vm, then that vm is used as a kvm host to run other vms via kvm. This way we can run exactly 100% the same image locally as is in production. In fact if you really want to do some crazy plumbing...
the VM host on my laptop has a VPN link to our DC, this puts it on the same internal network as our DC production hardware. I can then live migrate a production VM ( like a web front end ), onto my laptop, while it's fully operational doing processing for the production environment.
On my laptop it will still be, via VPN, receiving and processing live web requests on our website, and properly sending back data to the proxy and user. Not very performant, but the flexible plumbing is nice if you want to test/debug a clone of the exact production system locally. |