[CentOS] Server Virtualization

Tue Sep 18 23:31:12 UTC 2007
Flaherty, Patrick <pflaherty at wsi.com>

> I work for a school in a New Zealand university and we are 
> wanting to implement Server Virtualization for both CentOS 
> and Windows systems.  

Keep in mind virtualization software is moving pretty quickly. 8 months
ago Xen didn't migrate fully virtual hosts, now it does. In 5 years the
rediculous pricing structure for Virtualization technology will be gone
and virtulization will be a commodity where all you pay for are
accelorating drivers and managment tools. If you check the
virtualization page on wikipedia
you'll see a bunch of the questions you should ask to figure out your
reasons for going virtual. Try to rank the features you know will help
you frequently, and the stuff that's just "WOW! Moving a running server
is so cool!". Try to avoid cool stuff for cool stuffs sake. Live host
migrations are great if you have dynamic workloads or for the occasion
you need to take a physical machine down for firmware/hardware updates
during buisness hours, but think of how often you are going to use it
and what impact downtimes might have.

>  From my own research it seems that VMWare or Xen are really 
> the two major products to be considered, are there any others 
> I should be considering ?

Take a peak at KVM
(http://kvm.qumranet.com/kvmwiki/Guest_Support_Status). Might not be
ready for primetime, but it is pretty favored by the kernel maintainers
for simplicty and cleanliness so it's likely to end up going further
than Xen. Do you really think the hypervisors and managment software
isn't going to endup in hardware?

If it's "Enterprise Level Support" and performance you pretty much have
to go with VMware. Realistically, for most companies and workloads way
to many things are tagged as "Requiring Enterprise Class", and you can
get away with Xen and KVM. The free VMWare Server (aka GSX) is a
completely different beast from VMWare ESX, performs pretty terribly,
and is almost worthless for production servers. ESX is amazing, and I'd
recommend it if you have the money, but I it's like 3K every 2 sockets
and needs a san to be very useful. You can quickly rack up 50 grand in
hardware and licensing just to get off the ground.

If I had the time, I'd like to try using Xen with an OpenSolaris ZFS
iSCSI target as shared storage, but alas I do not have that time.
> Is anyone running Linux "Guest" O/S's inside a Windows host 
> ??  And if so can you share your reasons for this?

I've done for people I work with because cygwin is too much of a moving
target, or to test that their code compiles and works on both platforms.
I also sniffed alot of glue when I was younger.