Hypervisor

A hypervisor is software that facilitates virtualization of multiple operating systems on a single physical computer.

OSs installed under the hypervisor are called virtual machines (VMs) or guest OSs
OS expects exclusive access to resources such as the CPU, system memory, storage devices, and peripherals
- hypervisor emulates these resources and mediates access to the actual system hardware to avoid conflicts between the guest OSs
  - allows one physical server to run multiple virtual machines
  - enables a VM to run on any physical server
- VMs must be provided with drivers for the emulated hardware components
might be limited in terms of the different types of guest OSs it can support
enables moving VMs from one physical server to another
- good for high availability
components can be changed without need for in-person maintenance

Types of Hypervisor

aka bare metal virtual platform
hypervisor is installed directly onto the computer and manages access to the host hardware without going through a host OS
hardware needs to support only the base system requirements for the hypervisor plus resources for the type and number of guest OSs that will be installed
enables efficient use of resources
need to use remote management tool to interact with it
- provides a GUI containing details of the servers running and a means to configure them
E.g.,
- VMware ESXi® Server
- Microsoft’s Hyper-V®
- Citrix’s XEN Server

aka guest OS virtualization
hypervisor application is itself installed onto a host OS
- used in a guest OS (or host-based) system
must support the host OS
computer must have resources to run the:
- host OS
- hypervisor
- and guest operating systems
E.g.,
- VMware Workstation™
- Oracle® Virtual Box
- Parallels® Workstation