Considering that huge impact of virtualization technology in now a days IT infrastructure of any size. I decided to dedicate a small intro, and maybe it will follow some other posts, regarding basic knowledge of virtualization.
What is a virtual machine?
A virtual machine is a contrasted of a physical machine encapsulated as a set of files. In other words; A virtual machine is a software-defined computer that runs inside of another computer.
Virtual machines can use largely the same hardware as physicals computers, including network interface cards, hard drives, usb devices and SCSI devices (CD-ROM drives, tape drives, and scanners).
Why would we want to use a virtual Machine?
One of the main reasons is server consolidation. If we consider that a physical computer is typically using approximately 5-15% of its CPU power.
So if you decide to run multiple VM inside the same physical host, you could increase the CPU utilization up to 60-80%, of course not only the CPU but also the other resources as well.
Another good point is hardware independence, the same virtual machine can run on multiple hardware types without having to make any changes inside of the virtual machine.
A huge advantage is also that VMs are encapsulated as a set of files therefore they provide better mobility and duplication.
VMs also help you to reduce the downtime. Why? Because we can move a live running virtual machine from one host to another host. This basically means that HW maintenance operations do no longer require machine downtime.
VMs allow for automation development and production environments.