Virtualization, in the simplest form is running workloads in a virtual environment. It simulate or emulate physical resources in a virtual environment in order to achieve better utilization, faster deployment times and easier management.
We need a special software component called the Hypervisor in order to provide physical resources to virtualized workloads.
There are two types of Hypervisors,
- Type one hypervisor
- Type two hypervisor
Type one hypervisor
This type of hypervisors run directly on host hardware. So they are also called bare metal hypervisors or native hypervisors. Examples for these are,
- VMware ESX and ESXi
- Microsoft Hyper-V
- Red Hat Enterprise Virtualization (RHEV)
- Citrix XenServer
- Oracle VM
These hypervisors do not need an underline operating system to run and this reduce considerable amount of administration overhead and saves resources from host hardware.
Type two hypervisor
Hypervisors that needs a host operating system to run are identified as type two hypervisors. Following are few examples for type two hypervisors,
- VMware Workstation/Fusion
- Microsoft Virtual PC
- Oracle VM VirtualBox
- Oracle VM server for SPARC
Unlike in type one hypervisors, type two hypervisors need of host OS decrease host hardware resources available for gust VMs, increase complexity and manageability.
In most production environment we see more and more use of type one hypervisors rather than type two hypervisors due to the points mentioned above.
References:
- http://vapour-apps.com/what-is-hypervisor
- http://www.virtualizationsoftware.com/top-5-enterprise-type-1-hypervisors
- http://searchservervirtualization.techtarget.com/definition/virtualization
- https://www.networkworld.com/article/3234795/virtualization/what-is-virtualization-definition-virtual-machine-hypervisor.html
- https://www.redhat.com/en/topics/virtualization/what-is-virtualization
- https://docs.oracle.com/cd/E37707_01/html/E29665/hypervisorandldoms.html
