The Xen Summit

A few weeks ago I attended the Xen summit in Cambridge, UK. Xen is an open-source hypervisor project being driven by Ian Pratt from the University's Computer Laboratory. Xen is attracting a lot of interest as the de facto open source hypervisor for commodity hardware.

Xen is designed to be a thin layer of software which allows multiple kernels to run on a single machine. Among the many cool things this new layer of virtualization allows is OS checkpoint and resume, which the Xen team have used to good effect in their workload migration experiments. (I was at a Linuxworld BOF last March where the sound of jaws dropping as Ian presented their results was quite evident!) Take a look at the papers on their website - it's pretty cool stuff.

Xen is based on paravirtualization; that is, you have to make some changes to the low-level kernel to allow the OS to run. This is both because that was easier to do on existing x86 hardware, and more importantly, it's also better performing than other approaches.

Anyhow, we've been looking at Xen for about a year now, and recently a few of us have been working on a prototype port of Solaris to Xen on the x86 architecture. We're planning to make it work on x64 machines where we can exploit the new hardware virtualization technology as it becomes available. We're also planning to make the Solaris side of things into an OpenSolaris community project too; particularly since Xen is itself an open source project. Although we're still working on the mechanics of all that, I'd like to hear from people who want to participate.

Some of the comments below imply that you might think I'm only interested in help from kernel developers. I'm also interested to here from people who are already using Xen, and are prepared to experiment with, and give us feedback on, early alpha-class builds of Solaris on Xen too.

Another Update
The OpenSolaris on Xen community is now up: see the OpenSolaris web site to participate.

Technorati Tag: OpenSolaris
Technorati Tag: Solaris


Count me in! I've been chomping at the bit to see Solaris support for Xen..... even better would be a Solaris-based Xen hypervisor itself!

Posted by benr on May 10, 2005 at 08:28 AM PDT #

If the technology is real (I think it is...) and supportable (Novell thinks it is), I would love to encourage Sun to adopt this as one of the open source packages that they officially support (ala /usr/sfw). Excellent opportunity to give a quick answer to those saying "but zones don't do what VMWare ESX does."

Posted by Mike Gerdts on May 10, 2005 at 08:44 AM PDT #

Well, I'd certainly be interested, but I'm not sure how much I could help. I don't have much in the way of kernel coding skills.

Posted by brontitall on May 10, 2005 at 01:53 PM PDT #

I would love to see Sun port Xen to the SPARC v9 architecture (a lot of work, no doubt), but it would be cool. As I understand, with Intel's coming Vanderpool virtualization Technology, Xen may no longer require a modified kernel. That will put real pressure on VMware.

Posted by Mark on May 15, 2005 at 02:31 AM PDT #

Re the update: I'd love to help with testing. I actually don't currently use xen, but have a linux + freebsd project waiting for time. I'd like to be able to get solaris under that banner as well so I don't need to dual boot any more.

Posted by brontitall on May 18, 2005 at 09:33 PM PDT #

I'm also \*extremely\* interested in this possibility. Again, it's mostly a matter of letting me test cross-platform software without entirely losing all my hair. Solaris 10 on Xen is a developer's wet dream ;-) Any news on this now that OpenSolaris has gone live (at least the core bits)? I didn't find anything about Xen on the OpenSolaris site, and your weblog entry seems to be the main Google hit on the matter., btw (I'm not afraid of spam - you should see what I already get!).

Posted by Craig Ringer on June 14, 2005 at 09:37 PM PDT #

I'd like to be part of this effort too, I'm quite excited about OpenSolaris as it is, and would be more than willing to jump in. I don't know how much I could help tho' I haven't too much kernel coding skills. But do keep me posted ! Kumar

Posted by Krishna Kumar on June 15, 2005 at 07:12 PM PDT #

I'd be surprised if there weren't a good deal of interest in using OpenSolaris under Xen. Hopefully the necessary changes wouldn't be too difficult. I for one am eagerly awaiting being able to run a few solaris boxes on top of my existing (debian based) Xen installations.

Posted by Sam Johnston on June 16, 2005 at 10:20 PM PDT #

Can someone at SUN address the differences between the approach of Xin and others like VMware? Why is SUN focused on Xin instead of their Janus product? With Xin on Solaris 10 will a user be able to run a linux compiled application without starting some kind of interpreter? What about applications that require external system libraries?

Posted by Sid Wilroy on June 17, 2005 at 02:08 PM PDT #


I'm not from Sun, but I can answer your questions. First, Xen works like a more efficient version of VMWare that requires that the OS be modified to run in Xen. Each "child" OS appears to applications to be a full OS, and it basically is one, just without the lowest level hardware interfaces and with some memory management changes. There's more information at . The technical details are all on that site if you want them.

As for your second question, the way Xen works I don't see how you could run a linux app on Solaris without running a Xen instance of a Linux distro - essentially without running a copy of Linux in parallel with Solaris. It's definitely not the same as things like "Janus," lxrun, QEmu, etc.

Now ... time to get back to work. I hope there's a Xen project created on OpenSolaris soon...

Posted by Craig Ringer on June 18, 2005 at 04:37 AM PDT #

What approach are you taking? I think keeping Solaris 10 as the core controlling OS is a good idea. You can divide up the CPUs and other resources to your hearts content (ie. You have an 8 CPU system and want 5 dedicated to your database zone anytime it needs it. The rest of the time the other zones can use it. Easy to do under Solaris 10, impossible under VMware or XEN). Now can you keep that and run XEN as a zone-hypervisor (to run any OS inside). Let me know how I can help out. I've had very little development experience but I did get other OSes running inside a Solaris 10 zone (using bochs). Slow but it worked :)

Posted by tim on June 27, 2005 at 08:12 AM PDT #

Open Solaris running on Xen would be great , bye bye VM Ware ,Right now i got only Linux Kernels working on Xen , but seeing Solaris and Linux run on the same Hypervisor would be awesome.Please include my name in the team working on Solaris ports to Xen

Posted by Digvijoy Chatterjee on August 09, 2005 at 02:41 PM PDT #

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