Xen support in Fedora

[fasiha]

Xen support was made available in fedora8, that we don't see in newer versions like FC9, FC10 etc. Even installing FC11 with virtualization enabled it doesn't come as Dom0. Would it be an installation issue or Fedor doesn't come with that level's support to Xen? If yes why is that so?

[Rubberman]

Not sure, but I think that RH/Fedora is migrating to use of KVM instead of XEN for virtualization.

[fasiha]

Ahan, but why so? Do they have some licensing issue with xen? Or what else is the reason?

[Rubberman]

Don't know for sure, except xen does place some limitations on what the host can run. For example, I ran xen on my CentOS workstation originally, until I found that nVidia native drivers would not work with the xen kernel, and nVidia had no intention of supporting it, which is why I changed to use VirtualBox for my VM needs. Basically, I could use my system as a virtual machine host or I could use it for hi-res graphics and full-motion video, but I couldn't do both. Not an acceptable situation as far as I was concerned. So I looked at Parallels for Linux - no support at that time for 64bit hosts, and VMware - too expensive and a pita to use (compared to xen). VirtualBox combined the 64-bit host support with pretty good ease-of-use in setting up one's virtual machines, and the price was right (free), so I went that route. Basically I have been pretty happy with it with a few headaches, such as lack of 8-bit video support for Solaris x86 (needed for legacy apps) which meant that I had to update a bunch of software I was maintaining for my clients that used it to 24-bit color (conditional compilation), which was NOT a simple task, and one that I may or may not be recompensed for in the future...

Anyway, back to the subject at hand - why the move to KVM vs Xen? Honestly I don't know for sure, except that AFAIK the Kernel Virtual Machine code is getting into the base operating system kernel instead of an add-on as xen is - more on the lines of a built-in hypervisor, which would mean that things like nVidia drivers wouldn't need to be branched to support it and the standard kernel since it IS the standard kernel.

[bigtomrodney]

Xen required hosts to be modified. This was straightforward enough with Linux and other free systems. They developed the modifications for Microsoft Windows but were unable to release it due to licensing restrictions. KVM bypasses all of this.

Also, AMD and Intel both made huge CPU improvements that allowed virtualisation software to work better by allowing the code to run natively rather than through emulation. This meant that the performance benefits of Xen were not longer a factor.

Short answer, Xen requires modified guest systems and KVM does not.

[fasiha]

Xen requires modified guest systems and KVM does not.

You mean KVM only use fully virtualized Guest and not the Paravirtualized one??
n Thanks alot for information.

[bigtomrodney]

KVM has limited paravirtualisation support:

Kernel-based Virtual Machine (KVM) is a Linux kernel virtualization infrastructure. KVM currently supports native virtualization using Intel VT or AMD-V. Limited support for paravirtualization is also available for Linux guests and Windows in the form of a paravirtual network driver, a balloon driver to affect operation of the guest virtual memory manager, and CPU optimization for Linux guests.

Kernel-based Virtual Machine - Wikipedia, the free encyclopedia

[fasiha]

thanks alot to all