Why Xen to try out new distros?
 

Hi!

As I would quite like to try out a Debian-based distro while keeping my main distro, it has been suggested to me that I create a virtual machine with Xen and use that for the second distro.
But, what are the advantages - if any - of doing so, as opposed to the old-fashioned method?

As far as I can tell from the Xen docs, you would still have to create a separate partition for the virtual machine.

I haven't looked into Xen too closely, but with qemu you
can "install" another OS into a file (an image), much like
in VMWare.


Cheers,
Tink

no, you can run Xen from image files if you want, no need to turn over real disk to it.

The real advantage of xen is its cost (major expense if you use vmware) and the fact that it allows you to run more than one distro at a time. VMware supports Microsoft Operating Systems whereas, to my knowledge, xen doesn't - this doesn't mean that you can't use wine or codeweavers crossover to run windows apps. However, as in most of the virtual machine systems, high graphics 3D and AGPx8 are not well supported and sometimes impossible to achieve. So really virtualization is not, and has not been, designed with Gamers in mind.

That said, if you have sufficeint RAM, you can set up serious servers on different machines using different and customized distros, kernels and they can all be networked, or not, to try out pre-production systems (on one machine, such as a modern laptop) either for demonstration or development purposes. Most of the guests don't even need a GUI and they can be accessed and controlled from the host (xen dom0). So if you wanted to hide your database server, without internet access, behind a firewall that only allowed access from specific MAC address machines on your intranet, you can do so.

Furthermore, xen allows you to take snapshots of a virtual machine, and it is even possible to transfer a running virtual machine and all its data access from one physical computer to another in a different location. If you know what youy are doing!

I tend to like virtual machines because I don't have to reboot to change distros, I don't have to set up my printer for each and every distro, and I don't have to migrate my email and browser bookmarks and financial records from my main distro - yet they are always, instantly, accessible. It also means that you can happily do crazy things, experimental even, and if and when a machine 'blows up/crashes/panics' you just reload the snapshot (much quicker than reinstalling - usually under 5 minutes) and you try something completely different.

If you want to experience 'no fear' go virtual!

Edit:
PS: I haven't tried qemu, and all my VMware machines were on a Windows host. Since VMware want a separate subscription for a Linux based host I am switching over to xen 64-bit.

I have two debian sarge running in Xen 3.0, each of them are stored in one file for / of 1Gb and one file for swap of 512Mb.
It took me some time to make it run (problem of the guest OS kernel version and python too old) and now I'm in the phase of tweaking and performance testing. It gives very good results, its amazing.
I've heard that there is a less support/developpment for 64-bit architectures.

I installed Xen just the other day - haven't had time to find a work-a-round for the random ethernet MAC address issue yet, but I'll get there.
Thanks for your replies - they help putting Xen into perspective (now I actually think VMs might be pretty cool :))

Anyway, while it's true that Xen won't run Windows at the time of writing, this is apparently possible using the Vanderpool technology from Intel, which is supposed to be implemented in their next-gen CPUs... so, in a relatively near future, it will run Windows too. I came across an article on it - can't remember where though, but you can just google it.

as i understand it, Xen isn't supposed to be about compatability with existing architectures, it's about making the best virtual architecture the developers can for performance and reliability and such. If you want to make somethign like Xen be commonplace within enterprise level systems, you don't hack away at it to make it observe all of the i386's silliest quirks, or any other architecture, you say that you demand the right to be worth developing specifically for... so Xen doesn't emulate intel, or p series, it just is itself. well that's my take at least.