Hypervisors and you!

Daniel Fussell dfussell at byu.edu
Fri Mar 15 11:12:24 MDT 2013

On 03/15/2013 10:38 AM, Gabriel Gunderson wrote:
> On Fri, Mar 15, 2013 at 8:12 AM, Tod Hansmann<plug.org at todandlorna.com>  wrote:
>> - I'm looking at Xen, but don't know much about it yet
> Xen was the stuff back in the day. It's still widely used, but mostly
> by those with tons of existing investment and build out in their
> infrastructure. It was the obvious choice 7 or 8 years ago (has it
> really been that long?).
Xen still rocks.  With Citrix getting involved, things have changed; 
like the move to a Windows management client, and the fact that they 
over complicated XenServer/XenEnterprise and started charging as much as 
VMware.  But the Xen community stuff has been going strong for some 
time, and most of the new development happens there anyway.  Citrix has 
finally started opening up their Xen distro with the Xen Cloud Platform 
(XCP/XAPI), but I haven't had much success getting XAPI working in 
Debian.  It's still tied pretty heavily to CentOS.  There is command 
line management for XCP, but it's really complicated.  Every last piece 
has a giant UUID to specify, the documentation is not so thorough.  
There are some bash command completion for it now, but I still don't 
like it.  The plus side is, they have the signed paravirt drivers for 
windows in XCP without having to buy the big Citrix XenServer.  Other 
things I don't like about XCP are the reliance on the Microsoft VHD 
format and it's 2TB limit, and the scripts that used to all be in python 
are now all in ocaml.  I really don't see what that bought them that 
they didn't already have with python.  There is an open source Open Xen 
Manager client for linux that tried to duplicate the windows client, but 
it crashes often enough to be irritating, and it looks like it's gone stale.

Now that I've scared you away from XCP, the xen community stuff is still 
great.  I think the new Xen scripts are still in python, the XAPI has 
made it much easier to have it managed with Nova, or libvirt, or 
xenlight (the new community stack), etc.  Arbitrary python is no longer 
allowed in the config files, but I never really used that in the first 
place.  With xentools, I can have a nice, slim paravirt debian vm up in 
about 15 minutes, basically however long it takes rpm/debootstrap to 
pull the needed files from a repository.  Networking is now all handled 
by your distro scripts/configs (/etc/network/interface for debian).  I 
didn't like this at first, but once I ran through it the first time, I 
realized it was easier than the old network bridge scripts, and only 
slightly different than configuring additional ethernet cards anyway; so 
it's still nice and simple.

I started out running xen with virt-manager on SuSE, but found it much 
easier with just the standard command line xen stuff.  I tried to do 
libvirt a few times since, but often ran into things I could do easily 
with the xm command line interface that I couldn't do with libvirt.  I 
don't think I've missed much without libvirt.

;-Daniel Fussell

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