VMWare ESXi training - [2] Introduction to virtualization II

Types of virtualization

FULL VIRTUALIZATION 

• Full virtualization uses a special kind of software called a hypervisor. 
• The hypervisor interacts directly with the physical server's CPU and disk space. It serves as a platform for the virtual servers' operating systems. 
• The hypervisor keeps each virtual server completely independent and unaware of the other virtual servers running on the physical machine. 
• Each guest server runs on its own OS -- you can even have one guest running on Linux and another on Windows.

PARA VIRTUALIZATION 

• The para-virtualization approach is a little different than the full virtualization technique, the guest servers in a para-virtualization system are aware of one another.
• A para-virtualization hypervisor doesn't need as much processing power to manage the guest operating systems, because each OS is already aware of the demands the other operating systems are placing on the physical server. 
• The entire system works together as a cohesive unit.

O/S LEVEL VIRTUALIZATION

•     An OS-level virtualization approach doesn't use a hypervisor at all. Instead, the virtualization capability is part of the host OS, which performs all the functions of a fully virtualized hypervisor. The biggest limitation of this approach is that all the guest servers must run the same OS.

•     Each virtual server remains independent from all the others, but you can't mix and match operating systems among them. Because all the guest operating systems must be the same, this is called a homogeneous environment.