Difference between revisions of "Virtualization"

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(Example Software and hosters)
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=== Example Software and hosters ===
 
=== Example Software and hosters ===
  
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| '''Emulation''' || VMware, Qemu, Bochs ||
 
| '''Emulation''' || VMware, Qemu, Bochs ||
 
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Revision as of 03:05, 1 June 2015

Terminology

A hypervisor runs on the physical hardware. The hypervisor allocates (hardware) resources to different virtual machines, each containing a guest operating system.

Virtualization Methods

The three main methods of computer host virtualization are:

Virtualization/Emulation
Complete emulation of all hardware. This is slowest. Allows a hypervisor to emulate different a CPU for each guest OS.
Paravirtualization
The guest operating system runs on top of a small software API that closely mimics the underlying hardware, albeit in a jail. May be fast. Allows different operating systems to run in the same hypervisor.
Operating system-level virtualization
The guest and hypervisor run the same operating system. May be fastest, but also the least flexible.

Example Software and hosters

Emulation VMware, Qemu, Bochs
Paravirtualization Xen, KVM, bhyve, Wind River, Hyper-V?, VirtualBox?
Operating system-level virtualization chroot/jail, Linux VServer, OpenVZ/Virtuozzo, Docker, User Mode Linux.

Amazon uses Xen. Strato uses Virtuozzo.

Hardware-assisted virtualization

The speed of paravirtualization greatly benefits from hardware virtualization. Both Intel VT-x and AMD-V (released in 2006) allow the virtualization to run in hardware instead of software. This reduces the overhead and makes paravirtualization for guest OS almost as fast as the hypervisor OS.