Step back in time with me a couple of years, Xen was starting it’s upmars and with Xen paravirtualization became popular , then came the other Virtualization vendors and the discussion about which technology was best discussed started.
Now we all know that VMWare and Xensource were discussing how to include hooks for Paravirtualization into the Linux kernel and eventually that also happened,however there wasn’t really any adoption , a couple of weeks ago VMWare announced it was going to drop support for paravirtualization. Aparrently VMWare’s Paravirtualization story wasn’t really a success.
The Xen folks pioneered with Paravirtualization and a dedicated hypervisor, yet somehow also got interrested in running the Xen engine within an already existing operating system by means of a kernel module. That way Xen can also be run on different existing platforms just as KVM and Virtualbox, one of the big reasons for KVM adoption exactly is the fact that one can turn an existing Linux machine into a virtual machine host by doing a simple modprobe
However the initial development focus for Hosted Xen was Windows and OS/X
not really a market wher Open Source Virtualization tools are going to make big
adoption steps fast
So you might wonder who is using this Hosted Xen anyhow , apparently not that many people. On the other side there’s VMWare’s ParaVirt similar story
And who’s using ParaVirt ? Aparently nobody …as there used to be a huge performance bug in it for over a year ..
So the lesson learned ? Stick with your own mainline technology .. no need to
copy the others ideas, seems like they won’t be a success anyhow ..