Virtual Machine Technology

Virtual machine concept

Virtual machine concept

Virtual machine concept

VMM/Hypervisor

Host Resource

VM VM VM

Why virtual machine?Support multiple users On-demand computing environment creation & customization QoS guaranteed & performance isolationHigh availability Easy management Access “root” privilege …

CPU virtualizationFull virtualization OS Assisted Virtualization or ParavirtualizationHardware Assisted Virtualization

X86 architecture

Full Virtualization using Binary Translation

Paravirtualization(OS Assisted Virtualization)

Hardware Assisted Virtualization

Memory virtualization

Device and I/O Virtualization

Summary of virtualization technologies

Full Virtualization with Binary Translation

Hardware Assisted Virtualization OS Assisted Virtualization / Paravirtualization

Technology Binary Translation and Direct Execution

Exit to Root Mode on Privileged Instructions

Hypercalls

Guest Modification / Compatibility

Unmodified Guest OS Excellent compatibility

Unmodified Guest OSExcellent compatibility

Guest OS codified to issue Hypercalls so it can’t run on Native Hardware or other Hypervisors Poor compatibility; Not available on Windows OSes

Performance Good FairCurrent performance lags Binary Translation virtualization on various workloads but will improve over time

Better in certain cases

Product Vmware, Microsoft, parallels

Vmware, Microsoft, parallels,Xen

Vmware, Xen

Guest OS Hypervisor independent?

Yes Yes XenLinux runs only on Xen Hypervisor VMI-Linux is Hypervisor agnostic

Full virtualization: VMware workstation

Full virtualization: VMware ESX server

Paravirtualization: XenDifferent hardware components not fully emulated.

It only organizes the usages->near-native performance

Layout of a Xen based system: Privileged host system(Dom0) and unprivileged guest systems (DomU)

DomU are working cooperativelyGuest and host OS has to be adapted to XEN

(Kernel-Patch), but not the applications

Paravirtualization: Xen