Frequently asked question: My company is virtualizing our data center. Should we buy new servers or turn the ones we have into ESX servers?
My usual answer is a question: “How old are the servers you have?”
Average answer: “Somewhere around three years old.”
My reply: “Get new servers.”
Why new servers? Because, performance-wise, they smoke your old servers, and have all the new technologies like Extended Page Tables, VT-x, VT-d, etc. RAM is often a limiting factor for how many VMs you can get on a physical host. Newer servers can have lots of RAM on them, more inexpensively than old servers can have lots of RAM on them. New servers often come with four NICs built in — two for the service console, two for VMs. Older servers have two. And with new servers you won’t have to worry about them again for five years until the warranty expires. Your old servers have two years left on their warranty and extended warranties are expensive.
In short, take a look at what you’d spend to retrofit and then replace your old machines and compare that with the cost of new equipment over three to five years. It might be worth it, but in most cases the old machines are just sunk costs.