This is the approach used by the FreeBSD jails (http://www.
freebsd.org/) and Solaris10 zones (http://www.sun.com/software/
solaris/).
Hardware emulation introduces some overhead due to the translation of the requests
between the hardware and software. The paravirtualized solutions manage to
get a speed boost by eliminating the emulation steps. The operating system level
virtualization probably has the least overhead among the above three approaches
and is the fastest solution. However, it has a limitation that you can only run the
same operating system as the host. This takes away one of the great benefits of
virtualization, which is to provide users with the ability to run disparate
operating systems.
What is Xen?
Xen is an open-source paravirtualization technology that provides a platform for
running multiple operating systems in parallel on one physical hardware resource,
while providing close to native performance. Xen supports several operating
systems??”Linux, FreeBSD and NetBSD. The current version of Xen also supports
the new generation of AMD Pacifica and Intel VT-x chipsets and can run an OS on
these chips without any modifications by using a version of the hypervisor called
the Hardware Virtual Machine (HVM). HVM mediates between the guest operating
system and the hardware and passes on the calls made by the guest to the physical
hardware. So you can run Microsoft Windows on these chips using Xen!
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Chapter 1
[ 7 ]
Xen was originally developed in 2003 at the University of Cambridge Computer
Laboratory (http://www.
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