Hardware Virtualization or “Hypervisor” Technology is the most commonly encountered today and is best represented by Vsphere® by VMware, Inc. It is best understood to represent an operating software layer that allows multiple hosts to run concurrently on the same hardware. Each Virtual machine has it’s own CPU, Memory, I/O, etc. available to it’s operating system. No elements of the operating system are shared and each machine exists as a stand-alone server. The operating system software is unchanged from the traditional approach of a dedicated hardware machine except now multiple machines can share the same underlying hardware resources. Each virtual machine can even run different operating systems.
Operating System Virtualization is best represented by Parallels Virtuozzo® software. This software utilizes the base operating system in all virtual machines. So, Linux and Windows cannot be run on the same host machine. Each virtual machine can share the host hardware resources and operating system components. The end result is a fully functional standalone virtual machine that does not require the duplication of a hard disk image, operating system files, and RAM usage.