plus of being graphic for all configuration and its also generally the
current leader in virtual technologies on PC hardware. Xen is faster
overall but I've heard that VMware is faster on CPU instructions. The
problem is that part of the VMware license is that it won't let you
publish benchmarks. So its not easy to get access to independent tests
unless you do them yourself. I did some of my own tests before
implementing it at Suso and found that Xen is very fast. Nearly the
same as running on the hardware without going through Xen. On
paravirtualization, the CPU is about 5% slower than a native machine. I
haven't done any testing with full virtualization yet, but a guy from
Red Hat told me that full virtualization is faster on CPU instructions
and paravirt is faster overall (including I/O).
I tested CPU speed by running the Povray raytracer on several virtual
machines on the same physical machine and then determining the total
time based on work completed. Interestingly enough, the P4 that I was
using for it was most efficient not with one VM, but with about 12 VMs
running at once, all running the same job. Once I got to 16, it was less
efficient. Efficiency was somewhat of a bell curve. So at least with
Povray, if you wanted to render more in the same time, you should run 12
processes at once instead of 1 by 1 sequentially. As a side note, I
mentioned this to the Red Hat consultant that was here at Cook last
week, he went on to work at Dreamworks Animation this week, setting up a
render farm for their next 3D movie, and he is supposed to do it with
Xen virtual machines.
Xen is still a prominent project and should get some important
features in the next couple versions, like better hardware video
support, etc.
If you want something that makes it easier, you can try CentOS 5 or
RHEL 5 or Fedora 7, they all have a tool called virt-manager that does
things graphically. Honestly, I don't like it as well as the xm tool
because there is some functionality that is missing.
If you want to see Xen in action, go to any one of these sites and
you'll experience the end result of running Xen VMs.
All of these are completely on a VM:
http://www.straight2yourdoor.com/ (Bloomington-based delivery company)
These sites use databases that are on a VM:
http://www.londoncommons.net/ (Kinda slow because of the software
overhead for this site)
So its fast enough to be able to run production websites on. But the
biggest plus for me in using Xen is the ability to make template
machines. I can create a machine from a template in about 15-20
minutes. This is very useful for me at least if I need to move some
service off of a server. A real example of this is that I needed to
move the email database service off of the old shared user machine at
Suso, but I needed to be able to have MySQL 4.0, because that's what
this server runs, so I made a machine that just ran MySQL 4.0. If I had
to put MySQL 4.0 on some of my other newer machines, I would have run
into problems because I'm already using MySQL 5.0 on most of them.
So its highly useful. I've been working on a way of using Xen that I
call the Suso Xen Method (Of course), part of it is to use sparse disk
loopback files instead of LVM volumes on the root domain like some of
the tutorials recommend. I find using loopback files to be more
convenient and in my experience, there is hardly any performance loss.
I'll post to the list when I have it all written out.
Ok, I meant for this to be a lot shorter. :-(
Mark
On Mon, Jul 30, 2007 at 04:59:45PM GMT, Joe Auty [joe@netmusician.org] said the following:
> Hi,
>
> Other than the fact that under Intel XT compatible hardware Xen offers
> full hardware virtualization rather than the para-virtualization offered
> by VMWare and the like, what other sorts of advantages are there to
> running Xen? I don't really care about using my native video card in the
> OSes I want to virtualize.
>
> One of my reasons for asking is that it seems that setting up VMWare
> Player is much easier under Linux than Xen. I know that Xen was marketed
> as the next coming originally, but it seems like this excitement has
> died down?
>
> What is the current status with the Xen project, and are there plans to
> simply the setup process?
>
> I've never actually seen Xen in action, because it appears like the BIOS
> of this PC I'm on doesn't have an option to enable XT, and Xen is
> generating related error messages, so I kind of gave up on it thinking I
> wasn't going to gain much I couldn't get in VMWare. Should I give it
> another go? What is Xen like in managing these OSes, disk images, etc?
> I'd love to use an open source project for this sort of thing rather
> than VMWare.
>
> I ask the list because I know that there was either a Xen meeting (that
> I missed), or one planned (that I will surely make if I can). I would
> assume that this means that there are those on this list that know more
> than I about this project :)
>
> Anyone care to illuminate here?
>
>
> --
> Joe Auty
> NetMusician: web publishing software for musicians
> http://www.netmusician.org
> joe@netmusician.org
> _______________________________________________
> BLUG mailing list
> BLUG@linuxfan.com
> http://mailman.cs.indiana.edu/mailman/listinfo/blug
>
--
Mark Krenz
Bloomington Linux Users Group
http://www.bloomingtonlinux.org/
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