Hi guys. I'm at a nonprofit educational outfit here in Ottawa and for a few years my organization (the Canadian Math Socity) has been running two CentOS headless servers with Xen hypervisors on them. Each of these supports several virtual machines, which are all running CentOS as well. Now we're looking for the next generation upgrades, both hardware and platform and are looking for best current recommendations, with a heavy leaning towards open source options. Any comments or recommendations would be very helpful! First, we don't know if Xen (I'm talking about the freeware Xen) is still the best approach. Problems we've had are in terms of migrate-ability (our servers are partly intended to back one another up such that all the VMs could conceivably run under one metal box) and provisioning new VMs. There are a lot of other options I think, but we do want something quite solid for headless servers running in a rack. What would you do if you could re-start from scratch? Second, we would like to use something that can blend with cloud hosting as well (such that we could have VMs elsewhere, but managed by the same software on our site -- we are interested in getting into selling cloud hosting). Third, a related but separate question: What's the right way to run say a dozen CentOS VMs in production and yet keep all the patching up to date? We're always worried about updates and new versions to various installed products that will conflict with other installed products, yet not running the updates and patches would mean security holes that don't get filled and new features remain on the greener side of the fence. There's probably no magic bullet here, but what techniques do you guys use to keep your various VMs up to date without worrying about breaking systems? Is extensive testing environments the only option? Thanks guys! Steve La Rocque -- When everybody thinks the same, no one thinks at all. -Anon.