[Concept Learning] hypervisor

From Wikipedia: http://en.wikipedia.org/wiki/Hypervisor

1. Definition: A piece of computer software, firmware or hardware that creates and runs virtual machines.
Alias: Virtual Machine Manager (Vmm)

2. Two types of hypervisor (depending on whether or not they are directly running on the hardware)

• Type I: Runs directly on hardware, such as Citrix xenserver, VMWare ESX/esxi
• Type II: Run on the operating system, such as KVM

3.Paravirtualization
Guest operating-system to make system cils to the hypervisor, rather than executing machine I/O instructions that the hypervisor simulates.
Paravirtualization is a statement in xen. Other products have different names for this technology: a "hypercall" in parallels workstation, and a "diagnose code" in IBM's VM.