What follows is the continuation of my talk with Jim Klein, director of information services and technology for the Saugus Union School District in California. In this newsletter, we focus more on how the district has deployed the open source hypervisor.
What was the process? How did you bring Xen in?
We got Fedora 5 and we spent a lot of time hardening it and sorting out I/O issues and those sorts of things. At the time, we were migrating to the open source Zimbra collaboration suite and since people were expecting miscellaneous little problems anyway, we decided to virtualize Zimbra as our first production server. It was a high load situation. That one virtual machine is handling all the e-mail, collaboration and calendaring for everyone in the district. It was a really great acid test for us. We had that up by July 1, 2006. We ran on that for several months and then in October 2006 we started migrating our other district servers over [to Xen].
Did you run into any problems?
We didn’t really have any problems. There were some minor I/O bottlenecks and things like that, but the tough thing about Xen for us, and for most people as they’ve tried in the last year or so, was actually generating the virtual machines. Once you get the virtual domain set up, you have a working image and you can make a copy of it every time you need another one, so that’s really fast. But getting that initial set up was a little difficult because everything was command line based, there weren’t any great tools. Red Hat Enterprise Linux 5 [RHEL 5] offers some really enhanced and great tools that make generating virtual machines a piece of cake.
What percentage of the district’s servers is virtualized on Xen?
At the office, I’d say 70%. We do a lot of Linux and all of our Linux stuff is virtualized. We have a couple of Windows servers virtualized on Xen, as well, but they’re lighter loads, such as Web applications.
So what kind of consolidation or efficiency were you able to achieve with Xen?
We’ve got nine virtual servers across three blades. The big gain is that a virtualized machine is hardware agnostic so you can bounce it from box to box. So if we need more performance, we can bounce it to a machine that’s got more processing power. We’re doing that live with Xen, and it’s no cost because it’s open source. It also gives you the benefit of being able to handle hardware failures better. Zimbra, for example, runs on one virtual machine. Ordinarily, with such a mission critical application, I probably would have installed it on two separate servers in a cluster. Hardware failures are not such a big deal for me anymore because I’ve got all these blades and I can move a virtual machine really quickly if I need to.
Will RHEL 5 increase your efficiency by giving you more tools to manage the Xen vms?
The RHEL 5 tools are fantastic. It’s not that you can do more with them; it’s just that you can do things easier. For example, RHEL 5 has a nice graphical console that tells you what the loads are on all the vms across multiple boxes. Now, we have SNMP installed on all the virtual machines and we have to kind of track things in pieces.
Overall, how does Xen stack up with VMware?
Xen does the vast majority of what people want to do with virtualization. It doesn’t have some of the advanced functionality of VMware, but the bulk of the functionality that people need is there. I think Xen is moving along at the same speed as the rest of us are going. Most of us are getting into virtualization and want to do live migration, for instance, but we’re not quite at the point of resource scheduling. As more people start virtualizing x86 systems, I think Xen is going to catch up quickly.