UML vs. vserver vs. xen

[Adam Tworkowski]

Hey Dan,

I attempted something like this with xen several months ago on Sarge.  
My plan was to use a xen host which did nothing but act as a 
controller.  The guests were a firewall, fileserver (private) and 
mail/web server (dmz).  I would have to dig up my specs but LVM2 was 
also involved.  The guests seemed pretty heavily taxed (w/o any services 
running).  Typing had visible lag in the guest ttys.  My major gripe was 
the complexity with the networking which involved a mess of virtaul 
ether devices (dummy, bridged) to basically create a "switch".  I did 
manage to get it working (correctly) but when I went to move from drive 
set (raid1) from the temporary hardware to the final hardware, I faced 
some issues.  If I remember correctly the issues involved raid and lvm2 
and were not specifically Xen.  Because of this issue (which I could 
have recovered from) and with the relative "slowness" of the virtual 
servers, and the complexity of the network, made me question whether I 
really  wanted to  have  my "important" data  mail, photos, personal 
files, etc. host an a system that seemed to have so many possible points 
of failure.  I decided to shelve the project (temporarily) due to the 
performance hit and relative complexity in recovering from an issue. 

Adam

Daniel Armstrong wrote:

>I am looking to setup a box (Athlon XP +1800, 512MB RAM) as a home
>server, using Apache to host 1 or 2 websites, a MySQL database, email
>(Postfix or Exim), maybe learn more about DNS caching. Is anybody out
>there doing something similar implemented in 'virtual machines' using
>UML or vserver or xen?
>
>My original intention was to go with a minimal Debian 'stable'
>install, and add the necessary services one-by-one, but I am intrigued
>by some of the virtualization solutions available. It may be more work
>to setup UML or vserver or xen in the beginning, but it appears to
>offer greater flexibility to manage services and possibly greater
>security??
>
>What I want to do:
>
>- make use of a single server (Athlon XP +1800, 512MB RAM)
>- use debian 'stable' as the base install
>- use same version of debian for all the 'virtual' machines as well
>- a single admin (me)
>- no X server required
>
>Right now I am leaning towards the vserver option, as this way all the
>virtual machines make use of the single underlying kernel and I would
>think this makes a lighter demand on this older hardware as opposed to
>UML or xen, where every virtual machine has its own kernel. The
>trade-off is in robustness - if something goes wrong with your kernel,
>all your virtual machines are hosed.
>
>Anybody have any experience with the above-mentioned solutions and
>opinions to share? Or should I just keep it simple and have a single
>server that implements everything required?
>
>Thanks... Daniel
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