Using virtual machines is a great way to test new Lion Servers before putting them into production. You don’t have to dedicate a Mac to the task. You can run Lion Server (or Windows Server) in a virtual machine on any general-purpose Mac.

You can also use a single Mac to create multiple server configurations to test different settings, with different services turned on and different third-party applications installed. With virtual machines, you can test new versions of a server alongside the older versions in order to run comparisons.

You can add Lion and Windows clients in virtual machines and have a little test network all on one Mac, not connected to your real network. To do this without virtualization, you’d have to use multiple Macs, or a Mac with multiple hard drives or partitions. You’d have to reboot the Mac every time you needed to run a different configuration.

If you’re going to run your production server in a virtual machine, test it in one. After you get your test server configured and tweaked just as you like it, you can easily migrate it to a production server that you want to run in a virtual machine.

You don’t have to install server software and any extra applications and then configure it all over again. Just move the virtual machine files over to the server Mac.

When testing or setting up a server in a virtual machine, you can use a feature called a snapshot. It records the complete state of a virtual machine when you take the snapshot, including the software installed in the guest OS and the various server configurations.

You can revert to a snapshot if you decide you want to go back to an earlier configuration. You can have multiple snapshots as well. Keep in mind that each one can consume several gigabytes of disk space.