Forum OpenACS Q&A: Solaris Zones vs. Xen vs. Vanilla Debian

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I am starting a new OpenACS based project at the hospital I am working at and we are seriously considering going down the OS virtualization route. We have narrowed it down to Xen vs. Solaris Zones. I was wondering if there is any experience with Xen in the community?

I have gotten some initial feedback on Zones from the community (i.e. there is experience using them for OpenACS running PostgreSQL), but we would like to join the Debian install efforts that E-lane has spearheaded and Xen would allow that. As a side note: would also like to avoid trapping ourselves in the quirkiness of Solaris and the joy of installation that quirkiness brings with it).

Any feedback or thoughts are welcome.

Some Links:

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Posted by Jeff Davis on
Cathy Sarisky does virtualization for the developer hosting (developer plan) so it would be useful to hear what she is doing...
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Posted by Carl Robert Blesius on
I just spent some time talking with Zill from http://www.zill.net/ who has good experiences with Solaris Zones (processor hit for Zones is apparently around ~1-5% and there are excellent automation tools). As much as I like the sound of Solaris Zones, I still tend towards a solution that is more likely to get used by others and provide more flexibility long term.

I think Cathy is using User Mode Linux. I have ruled out UML based on research and problems getting a testing environment up.

Getting a test version of Xen running was simple ( http://www.cl.cam.ac.uk/Research/SRG/netos/xen/downloads.html ). In fact I had the Xen Demo up and running before I finished reading through the license and downloading the second Solaris 10 CD from Sun (iirc there where ~6).

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Posted by C. R. Oldham on
Actually, Cathy is using the Linux V-Server patches, not UML. See

http://linux-vserver.org/

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Posted by Dave Bauer on
And Cathy's thread http://openacs.org/forums/message-view?message_id=199180 describing her setup.
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Posted by mark dalrymple on
As a customer of Cathy's, living in a vServer, I'm a very happy camper. Any problems I've had with my sites have been my own stupidty (not testing boot scripts and the like)
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7: VServer vs. Xen (response to 4)
Posted by Carl Robert Blesius on
Link: Vserver vs. Xen

http://lists.xensource.com/archives/html/xen-devel/2005-02/msg00868.html

I like these two:

- move running virtual machines to another host without stopping them

- pickle a virtual machine's state to disk and resume it later (wonder if the paused server can be moved easily to another machine as well)

On the Vserver site I found this wish from Cathy:

"Biggest wish: more resource allocation abilities, especially for memory."

http://linux-vserver.org/VServer+Hosting

Is that still the case Cathy? This is one of the positive things I read about Solaris Zones (nice allocation between zones... e.g. if one zone needs RAM and anothers are not using it all, that machine can take adavantage of the situation). Wondering how Xen deals with this.

Also, here is a Xen limitation that could be important for heavy trafficked sites: "Xen can currently use up to 4GB of memory. It is possible for x86 machines to address up to 64GB of physical memory but there are no current plans to support these systems: The x86/64 port is the planned route to supporting larger memory sizes." How much RAM does a site like Galileo typically need? On the other hand, we do have a load balancer for clinical applications and could possibly use it to distribute load to various Xen instances on different physical boxes.

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Posted by Andrew Piskorski on
I've heard very good reports on Xen from some who are using it. I never heard of Solaris Zones until now, but my first thought is, why lock yourself into Solaris?

Solaris Zones sounds like Linux V-Server or the FreeBSD Jail facility. These are all inherently different than Xen. With Xen you can run multiple different kernels, even entirely different operating systems (as long as they support Xen). The new thing about Xen, is that unlike VMware, it can do this efficiently (like IBM's VM) on commodity processors (unlike IBM's VM).

See also these old threads: 2004-02, 2003-06, 2003-02.

The problem with Debian, currently, is that there is no support for x86-64 (neither AMD nor Intel) in Sarge. So either you run 32 bit x86 Debian, or you use the unofficial (and "unstable") Debian AMD64 port. Neither of which is a particularly good choice for people buying x86-64 servers now...

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Posted by russell muetzelfeldt on
With Xen you can run multiple different kernels, even entirely different operating systems (as long as they support Xen).

Depending on your requirements this can be a good thing or a bad thing. Do you actually need to run several different OSs or OS versions on your production servers? If not then virtualisation along the Zones/Jail line is actually a win since you don't have the resource hit (memory mainly, but also cycles) of running multiple kernel images at the same time.

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Posted by John Sequeira on
The new thing about Xen, is that unlike VMware, it can do this efficiently (like IBM's VM) on commodity processors (unlike IBM's VM).

Andrew, although VMWare's overhead is more than Xen's, it's still pretty good. I believe the rule of thumb is ~15-20%, so maybe your 3Ghz Xeon behaves like a 2Ghz Xeon. Not a difference that should really matter if you're not running at the limit of the machine.

For real world experience, I deployed half of my projects last year into VMs on client's sites. These were decent size intranet apps (100s or 1000s of users). It worked great -- often I found out late in the project that the machine I was remote'ing into was a VM.

The only issues encountered with the rollouts were developer inflicted. :-)

Anyway, here's a great article contrasting the different approaches:

http://www.computerworld.com/hardwaretopics/hardware/server/story/0,10801,101243,00.html