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Xen 2.0 Virtual Machine Monitor Released

Posted by michael on from the xen-and-the-art-of-system-maintenance dept.

An anonymous reader writes "The Xen team are pleased to announce the release of Xen 2.0, the open-source Virtual Machine Monitor. Xen enables you to run multiple operating systems images concurrently on the same hardware, securely partitioning the resources of the machine between them. Xen uses a technique called 'para-virtualization' to achieve very low performance overhead -- typically just a few percent relative to native. This new release provides kernel support for Linux 2.4.27/2.6.9 and NetBSD, with FreeBSD and Plan9 to follow in the next few weeks. Xen 2.0 runs on almost the entire set of modern x86 hardware supported by Linux, and is easy to 'drop-in' to an existing Linux installation. The new release has a lot more flexibility in how guest OS virtual I/O devices are configured. For example, you can configure arbitrary firewalling, bridging and routing of guest virtual network interfaces, and use copy-on-write LVM volumes or loopback files for storing guest OS disk images. Another new feature is 'live migration', which allows running OS images to be moved between nodes in a cluster without having to stop them. Visit the Xen homepage for downloads and documentation."

21 of 199 comments (clear)

  1. Xen 2.0 Koan by gowen · · Score: 5, Funny

    What is the sound of one hand crashing?

    --
    Athletic Scholarships to universities make as much sense as academic scholarships to sports teams.
  2. Alas, no Windows... by October_30th · · Score: 5, Interesting
    A port of Windows XP was developed for an earlier version of Xen, but is not available for release due to licensce restrictions

    Sigh... how hard would it be to get a license and distribute it as a binary-only module to people like me who'd be willing to pay for it? I'm sure it'd still be less expensive than the existing alternatives.

    Otherwise this looks very nice. In fact, I didn't know that there was such a mature free virtual machine available.

    --
    The owls are not what they seem
    1. Re:Alas, no Windows... by Frasier · · Score: 4, Interesting

      Sigh... how hard would it be to get a license and distribute it as a binary-only module to people like me who'd be willing to pay for it?

      Microsoft has their own virtual server product. They propably do not want competition, especially something that allows one to run Windows XP and Linux on the same machine at the same time.

      I would personally love to have access to a Windows system without having to dedicate entire machine for it. But Microsoft has not, is not, and propably will not show any signs of willingness to cooperate with non-Microsoft systems.

    2. Re:Alas, no Windows... by julesh · · Score: 4, Informative

      VMware developers must have bought a license, so what's the problem here?

      VMware runs an unmodified version of Windows by presenting a virtual machine that is practically indistinguishable from a real PC. Therefore they don't need a license.

    3. Re:Alas, no Windows... by ColdGrits · · Score: 4, Funny
      VirtualPC runs Linux like crap. The sound doesn't work and is less than stable.

      Sounds like the emulation is pretty accurate then! ;-)

      (Oh c'mon, lighten up, it's a joke...)

      --
      People should not be afraid of their governments - Governments should be afraid of their people.
  3. Obligotory. by Anonymous Coward · · Score: 5, Funny

    Oh man, can you imagine the overhead on a virtual beowulf cluster using this?

  4. It's not really useful if... by spidergoat2 · · Score: 4, Funny

    It can't run AmigaDOS.

    1. Re:It's not really useful if... by Zorilla · · Score: 4, Funny

      Yeah, I agree. These guys missed a huge user base by completely missing the point of running virtual machines. It looks like I'm still stuck in the mud until someone develops a solution to get all my TRS-80 apps working again.

      (Note to mods: take a joke)

      --

      It would be cool if it didn't suck.
  5. Since we all love screenshots... by Zemplar · · Score: 5, Informative

    Direct link: http://www.cl.cam.ac.uk/Research/SRG/netos/xen/scr eenshots/index.html

  6. Re:And the point of this application is.. by grub · · Score: 5, Informative


    Let's assume you're an ISP and have a few big machines on the racks. Your customers don't want or need that much horsepower but want their webserver (which you maintain) to run under Linux, or NetBSD, or FreeBSD, or whatever.. You can do it.

    Let's assume you're a developer and want to test your code under various OSs, now you can do it on the same box in realtime (read: no reboots)

    The list goes on and on, it's a great technology.

    --
    Trolling is a art,
  7. Great for free "UX's" but not for Win32 by slashnik · · Score: 5, Informative

    from http://www.cl.cam.ac.uk/Research/SRG/netos/xen/faq .html

    1.3 Which OSes run on Xen?
    To achieve such high performance, Xen requires that OSes are ported to run on it. So far we have stable ports of Linux 2.4, Linux 2.6, and NetBSD. Ports of FreeBSD and Plan 9 are nearing completion.

  8. Re:64 bit? by julesh · · Score: 5, Informative

    From the manual:

    A port specifically for x86/64 is in progress, although Xen already runs on such systems in 32-bit legacy mode

  9. Not as cool. by Anonymous Coward · · Score: 5, Informative

    From the FAQ, it states that you can only run OS's ported to it. While this might be great for cluster testing, or software design, this is defintely no VMware replacement. I am slightly disappointed in this, but I can see where it has its place.

  10. Re:And the point of this application is.. by Anonymous Coward · · Score: 5, Interesting

    Actually, a couple ISPs and datacenters are already working on using Xen for this exact purpose.

    http://xen.terrabox.com will be back online in the next 72 hours. You can find a wiki about xen there. One page is available for listing of any companies that offer Xen based virtual servers. So far the customers that i have setup under Xen have been quite impresed with the speed and stability as compared to the traditional virtualized and meta-virtualied linux vhost setups. :)

  11. This is a VM platform, not a VMWare competitor by ites · · Score: 5, Interesting

    Big difference. VMWare is about virtualising a foreign OS. Since VMWare abstracts at the BIOS and hardware level it can run almost all OSes the CPU will support but it takes a large performance hit.

    Xen is a VM platform, i.e. it lets you set up multiple virtual machines that run with very little extra overhead. A lot like User Mode Linux, except easier to configure and install.

    Here's a typical use case: you want to make a network "security box" that includes firewall, proxy, web server, email, wiki, irc. Now, conventionally you put all these services in the same Linux system (or whatever OS you use). Using Xen you run all of the services in their own virtual machine, so that if the firewall gets compromised, for instance, an attacker cannot get access to other parts of your system.

    It's a very useful tool.

    Oh, another use case I just thought of too: how about a 'hidden' Linux OS on your Windows box that does all your email, browsing, and other Internet work that you want to keep secure. Click the icon, up pops Mozilla, except it's running in a different virtual OS.

    Yup, definitely very useful.

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    1. Re:This is a VM platform, not a VMWare competitor by Anthony+Liguori · · Score: 4, Insightful

      VMWare is about virtualising a foreign OS. Since VMWare abstracts at the BIOS and hardware level it can run almost all OSes the CPU will support but it takes a large performance hit. Hehe.. The VMWare marketing guys have gotten you pretty good. What your describing is something called full virtualization. It's what IBM does in PowerPC (with something like the OpenPower platform) and with hardware support can be pretty darn fast. The IA-32 architecture is not capable of full virtualization. If you don't believe me, just read any of the dozens of papers written on the topic. Memory poses a problem (albiet one that's overcomable) but the thing that makes it impossible is the behavior of three instructions. Virtualization's really a simple concept. You run an OS at a lower priviledge than it expects and the priviledged instructions will throw exceptions that can be caught and emulated. Certain instructions on IA-32 silently fail when executed outside of ring 0 making it impossible to emulate those instructions. What tools like VMWare do is run through the executable and change those instructions to illegal instructions or do dynamic rewriting of the executable. That's right, they have to dynamically rewrite the executable. Have you ever wondered why VMWare asks you what OS it will be running? Because it has a big set of tables of where instructions need to be rewritten. Have you ever tried to run a checked build of Windows in VMWare or better yet a newer version of Windows that just isn't supported? It fails miserably. The difference between VMWare and Xen is that Xen accepts the difficulties and then decides that if we're already going to change the OS, let's just make a few more changes to improve performance. Adding VMWare-style virtualization support to Xen wouldn't be that difficult if you have the tables and such that VMWare had. Remember too, VMWare requires OS-drivers to be installed.. there's a reason for that.

    2. Re:This is a VM platform, not a VMWare competitor by TimMann · · Score: 5, Insightful

      You're largely (though not entirely) mistaken about how VMware virtual machines work. User code runs in direct execution up to where it tries to make a system call or takes a page fault (etc.) and traps into privileged code. Privileged code is *dynamically* translated at runtime; we don't have big tables that tell us exactly where all the instructions in each supported operating system need to be patched. That would be totally impractical.

      We ask what guest OS you're running because we have certain OS-specific optimizations, things that help one OS a lot while hurting others. Most OSes will run fine (though more slowly) on the "other" OS setting. A small number need specific workarounds that are enabled only if you select the right OS setting.

      Checked Windows builds work fine AFIAK. If you have one that doesn't work, file a bug report. New OS versions usually work without VMware changes, though not always. Sometimes they'll exercise a system feature that is slow until we optimize it more in the next release, or sometimes their drivers will try to use a device in a new way that our emulation of it doesn't yet support.

      We do supply some device drivers for guest OSes, not to work around any shortcomings in our CPU virtualization, but because for performance reasons some of the virtual hardware we implement is not the same as any real hardware that the guest has its own drivers for. The only such devices are the virtual display card (which works as a standard VESA device even if you don't install our driver, albeit slowly), one of the two virtual ethernet cards we support (the other is a standard though elderly AMD card), and one of the two pointing devices (the other is a standard PS/2 mouse). Hmm, I think we also supply some SCSI drivers, but only because some guest OSes don't have good drivers for either of the two standard SCSI cards we emulate (one from BusLogic and one from LSI Logic).

      As you can guess from the above, I work for VMware -- in engineering if that makes me more believable to you, although I haven't encountered our marketing folks lying. Standard disclaimer: I'm speaking only for myself here, not officially for VMware.

  12. Re:versus UML? by Anonymous Coward · · Score: 5, Insightful

    UML has MASSIVE context switching overhead.
    UML runs insidethe host OS and thus is a security risk.
    UML doesn't access hardware via native drivers (PCI hardware that is).
    UML is DOG slow compared to xen domains for IO.

    I could go on. UML is/was a good solution, but if you wanted a BSD, plan9, or other OS trunnign on the same hardware as linux, forget it.

    Under Xen, you can run 1 domain that uses hda, hdb, and the USB stuff directly, a second accesses a second IDE set at hde and hdf and a second PCI video card.

    Remembers, xen isn't about just launchign another OS, it's about splitting up the hardware in a secure fashion. :)

  13. Absolutely cool tech! by a_hofmann · · Score: 4, Interesting

    GPLed virtualization software that according to the benchmarks achieves performance unseen in current approaches - sounds like a dream come true.

    It would be astonishing if those benchmark numbers hold true in a production environment, which might well be as the selected benchmarks (SPECint, Postgres, Apache, ..) should give a fair picture of the overall performance hit for the virtualized systems.

    Being able to partition your OS without serious performance implication would open a whole lot of new possibilities for developers that previously where only possible with huge investments in high-end hardware and expensive virtualization software licenses.

    I've already decided: My price for the most useful opensourced application in 2004 goes to..... Xen :)

  14. QEMU by nns6561 · · Score: 4, Informative

    QEMU is a similar open source project. It's supposed to run unmodified versions of Windows even. Does anybody know what QEMU's lastest performance numbers are?

  15. Re:Steal or Deal? by Frasier · · Score: 5, Insightful

    Microsoft Research operates fairly independently and it's focus is in research, not product development. They publish papers and their projects are reasonably open but that openness has mostly not carried over to Microsoft itself.