Xen Virtualization

[Fernando Duran]

Hello,

Just some quick notes on my experience with Xen. One
of the companies I work for (rimuhosting.com) was one
of the first in offering Linux virtualization for web
hosting; starting with UML and then with Xen.

The summary is that using Xen has been very
successful: from the business/consumer point of view
you can get a Virtual Private Server with all the
goodies of a dedicated server (full root access, own
separated filessytem etc) at a small price.
Technically it makes possible to add some unique
features like full automated snapshot backups,
console-over-ssh or easy VPS reinstalls.

As it has been commented (I think), virtualization
offers many advantages like added security, easier
management, failure isolation etc. So in fact we're
offering the customers that want a dedicated server
from us that they can also get it with Xen, so they
can have the features mentioned before.

On the Xen downside, there are a couple of them. Of
course there's some overhead, although little (not
sure where the figure comes from but I'm reading
3-5%).

In the VPS you give up direct access to hardware
(usually not a problem) and running modules (if you
want to able to recompile a new kernel without messing
the settigns in the VPS'), although in our case most
of them are built in the kernel or we can add them per
a customer's request.

Also while many web sites/services run happily with
small memory (typical LAMP apps, mail etc), there are
stacks or apps that consume quite a bit of memory,
like anything using Java (tomcat/jboss etc), so
sometimes they need an amount of memory that starts to
compare with a dedicated server.  Also a VPS' memory
in Xen is fixed while running (it can be easily
changed in a reboot), unlike other hypervisors
(virtuozzo?) that allow for memory bursting (but that
can lead to oversubscribing abuse too). 

Finally, and depending on the version of Xen, from
time to time Xen hits some kernel bug and the server
needs to be rebooted, so it may not be suitable for
very high available servers.


Regards,

Fernando Duran
http://www.fduran.com

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com 
--
The Toronto Linux Users Group.      Meetings: http://gtalug.org/
TLUG requests: Linux topics, No HTML, wrap text below 80 columns
How to UNSUBSCRIBE: http://gtalug.org/wiki/Mailing_lists