Recently, Cisco started saying that virtualization doesn't actually save money due to increased management costs involved with running a virtual infrastructure. Sure, in the same glossy Cisco was selling its "unified computing" system and management tools, but it may have had a point. Sometimes it may seem like running a virtualized environment is more work.
It's certainly different, which means there is a one-time learning curve. The ramp-up costs associated with learning management tools for a given virtualization environment are one-time costs, or sunk costs, that wouldn't factor into the calculation of yearly IT management costs.
There are fundamental differences in the way virtualized servers are managed, however. If these differences, compared to running bare-metal servers, prove to add a substantial management overhead, there may be something to this notion. Let's talk about four aspects of managing a virtual environment: deployment, managing changes, monitoring and tuning.
A deployment server for physical and virtual machines is the same thing: a network boot image that starts the kickstart (or FAI, or jumpstart) process, and configures a minimal environment. Most often it sets up the configuration management software, so that when the new OS is booted for the first time it will fetch its configuration from a central server and apply whatever changes are necessary.
Deploying virtual machines is a tad different, in reality. Your deployment system needs to be aware of the virtual environment, and it needs to know how to configure Xen or KVM's storage and other critical details (VMware has its own thing that handles everything for you). Using Cobbler , you can deploy virtual machines with a single command, and it centralizes all your kickstart configurations for easy management of all physical and virtual machines. Regardless of the chosen tool, they exist and make deployments very easy.
After initial deployment, maintaining changes across all these new servers is really no different. You have global configuration updates that need to go everywhere, including the virtual machines. Some virtual machines will be grouped together for various configurations, such as the services they run, and you're still only making changes in one place (your configuration management tool). When the number of virtual machines grows due to the number of applications growing, you're going to need to evaluate whether or not a new virtual machine is warranted; more on that in a moment.
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