3aIT Blog

This month, we'll take a look at exactly what a Virtual Machine (Or "VM") is, and why you might want to use one.

In this case, the explanation of what a virtual machine is is very simple. The name is very apt. It's a PC / server that doesn't exist in a physical form. Instead, it is emulated by software on a server. This server is usually capable of running many of these machines. However, to a user logging into the machine, it appears fully functional and mostly indiscernable from a "real" machine.

So that explains what a virtual machine is, but why use them? The biggest advantage is the hardware cost is lowered. It's often the case that any one machine is only using a fraction of its available resources at any one time. If this machine exists as a physical standalone device, there's not much that can be done about this. However, if this machine is a virtual device on a server that also hosts other virtual devices, those idle resources can be allocated elsewhere.

For instance, you may have a backup server that takes a complete copy of your company's data every night. If this server existed as a physical box, it would be sitting around doing nothing at all during the day. As a virtual machine, it can exist on "life support" during the day, and then given extra oomph at night when the backup is being run. This extra power can be allocated from other company servers which will be far less in demand during the night.

The other big advantage of virtual machines is that as they only exist as data on a server, it can be treated as any data can. One can move it to another server, create complete backups and copies can be made for testing new software before a rollout. Also, virtual hardware cannot fail, so individual virtual machines will never die (software issues aside).

Of course, the server that's running all the virtual machines CAN fail. If the host machine fails, all the virtual machines that it is running go down with it. Thefore, it's useful that backups of the machines are so simple! In a worst case scenario, these backups could be transferred to a new host, and all the virtual machines would be back and running exactly as they were.