In a DevOps initiative how critical is it that the lower environments (i.e., non-production) be virtual (as opposed to dedicated) in terms of being able to quickly stand-up, test and tear-down these environments after a build and deploy?
In a former incarnation of mine, we had a complete replica of our production facilities: database server and test webapp server. Originally this was all dedicated hardware, until circuit breakers because we had whole racks full of equipment sitting idle much of the time, including production machines whose CPU usage rarely topped 15% but had to be isolated from less-sensitive systems. At that point, I did some work towards getting Solaris Zones running on some of the machines, as it was a very efficient alternative.
Stuff I'm doing these days tends to be a lot more experimental and for that, environments like Vagrant are invaluable. Even for some of my older projects it would have been nice if I could bring up a dedicated VM, pollute it with experimental products, then blow it away once I'd learned what not to do. Vagrant/packer and Docker plus provisioning systems such as puppet, chef, ansible, and salt mean that I can get a lot of stuff pre-made so I don't have to start from scratch to spin up a development, test, or production system - and, for that matter, one of each using the same basis. And storing configurations rather than full disk images is a lot more conservative of resources, even when your desktop machine has a 3TB hard drive.
Depending on load dynamics, an in-house private cloud can also make sense. VM hosts are all well and good, but a full-on cloud makes it possible to move VMs around in order to make optimal use of hardware resources. You can also exploit virtual private (software-defined) networks within the cloud so that an extra layer of isolation is maintained between systems without the bother of having a tech jack into the corporate routers - and possibly bring down unrelated network functions on a massive scale.
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