OS Virtualization

Sometimes called OS-level or shared OS virtualization, OS virtualization virtualizes servers on the operating system (kernel) layer. This method of virtualization creates isolated partitions, or virtual environments (VEs) on a single physical server and OS instance to utilize hardware, software, data center and management efforts with maximum efficiency.

The two diagrams below show the hypervisor or hardware virtualization technology in comparison to OS virtualization.

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The hypervisor model has a base layer (usually a thin Linux kernel shown here as a hypervisor or standard OS) that is loaded directly on the bare server. To allocate hardware and resources to the virtual machines, all of the hardware on the server must be virtualized. The next layer up shows each chip, board, etc. must be virtualized so that it can be assigned to virtual machines. Once in the virtual machine itself, there is a complete copy of an operating system and finally the application or workload.

The OS virtualization model is streamlined for the best performance, management and efficiency. At the base resides a standard host operating system, in the case of Virtuozzo that includes Windows and Linux. Next is the virtualization layer with a proprietary file system and a kernel service abstraction layer that ensure isolation and security of resources between different virtual environments. The virtualization layer makes each virtual environment appear as a standalone server. Finally, the virtual environment itself houses the application or workload.