Become a fan of Slashdot on Facebook

 



Forgot your password?
typodupeerror
Operating Systems Software

Performance Evaluation of Xen Vs. OpenVZ 116

Posted by kdawson
from the price-to-pay dept.
An anonymous reader writes "Compared to an operating-system-level virtualization technology like OpenVZ, Xen — a hypervisor-level virtualization technology that allows multiple operating systems to be run with and without para-virtualization — trades off performance for much better isolation and security. OpenVZ's performance advantage due to running virtual containers in a single operating system kernel can be significant. A performance evaluation study (PDF) done by researchers at the University of Michigan and HP labs provides insight into how big a performance penalty Zen pays and what causes the overheads (primarily L2 cache misses)." From the report: "We compare both technologies with a base system in terms of application performance, resource consumption, scalability, low-level system metrics like cache misses and virtualization-specific metrics like Domain-0 consumption in Xen. Our experiments indicate that the average response time can increase by over 400% in Xen and only a modest 100% in OpenVZ as the number of application instances grows from one to four... A similar trend is observed in CPU consumptions of virtual containers."
This discussion has been archived. No new comments can be posted.

Performance Evaluation of Xen Vs. OpenVZ

Comments Filter:
  • Which I'm sure is feeling the heat from Xen.
    • I assume that most of these different approaches to virtualization will run some versions of the Linux kernel as a client, perhaps even most versions, and that you can talk BSDs into running on them as well (though it'd be particularly nice to know whether OpenBSD runs on them), and that you can run most of them on top of most Linuxes and maybe most BSDs (again, OpenBSD's the interesting one, due to security).

      But which ones of these things can run Windows clients, at least XP? VMWare can, User Mode Linux

      • Re: (Score:3, Informative)

        by DrSkwid (118965)
        qemu runs Win2k. My AMDX2 3800 runs it using kqemu. I happily use it for testing things in I.E. It seems about as fast as my PIII 1Ghz laptop, though I've never actually measured it.
      • by ppadala (220707)
        > But which ones of these things can run Windows clients, at least XP?
        > VMWare can, User Mode Linux can't, but what about OpenVZ, Xen, and some of the others?

        Xen can run Windows without para virtualization using new processor VT extensions. OpenVZ's commercial implementation Virtuozzo can run Windows on Linux.

        > do any of these make USB devices visible to the client OS?
        > Or do they all just have to network-mount resources that are actually mounted in the host OS?

        Both Xen, VMware and OpenVZ all al
    • FWIW.

      I am a big fan of Virtuozzo and OpenVZ. I just wish vzstat would be included with the free stuff.

  • Stop the press (Score:3, Insightful)

    by general_boy (635045) on Monday May 14, 2007 @08:39PM (#19124585)
    [Xen]... "trades off performance for much better isolation and security."

    No kidding, that's why I use it! Xen's performance ain't so bad. Show me a better performing virtualization solution that matches or bests Xen's isolation security - then we'll talk.
    • by vrmlguy (120854)
      VMware? (Hey, you didn't say "free", although VMware Player and VMware Server are free-as-in-beer.)
    • Re:Stop the press (Score:5, Insightful)

      by jambarama (784670) <{jambarama} {at} {gmail.com}> on Monday May 14, 2007 @11:30PM (#19125885) Homepage Journal
      Yeah but Xen is still a royal PITA to get running. KVM wasn't bad, and VMWare was pretty easy. I haven't even seen OpenVZ. Of the three I've tried, the ease of use was highly correlated to the product maturity. All three work, but IMHO VMWare is so far ahead it will take some time for Xen to be considered out of the hobbyist market and in the commercial one. I'm sure it'll get there, but to do what? Be a faster VMWare?

      So to sum, we've got OpenVZ, Virtualbox, KVM/Qemu, Xen, VMWare, Virtual Iron, and Virtuozzo. With so much virtualization software, I personally think performance takes a back seat to functionality (sure OpenVZ is fast, cool, what will it do for me that VMWare or Xen won't?). Is there really that much space in the virtualization landscape?
      • Re: (Score:3, Interesting)

        by wertarbyte (811674)

        Yeah but Xen is still a royal PITA to get running.
        apt-get install xen-linux-system-2.6.18-4-xen-686 xen-create-image --hostname ........ done. Looks quite easy to me.
        • by stevey (64018)

          Nice to see you pimping xen-tools [xen-tools.org] :)

        • xen-create-image --hostname ........ done. Looks quite easy to me.

          Now, you see, I've actually used xen-tools and I notice that you've cunningly left out the part where you edit /etc/xen-tools/xen-tools.conf

          because what you get when you *don't* edit that config file to suit is this (for example):

          The kernel image we're trying to use does not exist.
          The image is - /boot/vmlinuz-2.6.16-2-xen-686
          Aborting


          ie the default config file for the current version of xen-tools points to the wrong kernel. And thats just for
        • by drsmithy (35869)

          Looks quite easy to me.

          That's because you're not doing anything interesting.

          Try working with multiple vlans, bonded interfaces, multiple drives in VMs, SANs, etc, then come back.

          • I never had an issue with multiple drives in Xen.

            What drives me up the wall at the moment is bonded interfaces. The Xen scripts flat out suck for doing any sort of ethernet bonding in domain0.
      • Re:Stop the press (Score:5, Interesting)

        by Xouba (456926) on Tuesday May 15, 2007 @02:55AM (#19127055) Homepage

        Yeah but Xen is still a royal PITA to get running. KVM wasn't bad, and VMWare was pretty easy. I haven't even seen OpenVZ.

        Yes, Xen is harder to install. But to compare it with KVM ... did you try to use them? KVM (at least, last time I tried -- which was only a couple weeks ago) is still in development, and the performance is so low compared to Xen that it's not even funny.

        On the other hand, VMware is very nice, specially the free Server edition, and it's really easy to use. But even so, performance is better in Xen. Check this [xensource.com]. Paravirtualization needs modified guests, but the outcome is so good that VMware is trying paravirtualization too [vmware.com].

        VMWare is so far ahead it will take some time for Xen to be considered out of the hobbyist market and in the commercial one

        What do you think is needed for Xen to be considered apt for commercial use? Remember that Xen can use unmodified guests if the hardware supports VTX/SVM instructions, which means that it can run Windows. Pretty front-ends? Xensource (which is slashdotted now, I guess, because it times out from here) offers one, and you also have Enomalism [enomalism.com].

        Besides, by what Wikipedia says about OpenVZ [wikipedia.org], it seems to be more a solution like jails [wikipedia.org], because it uses the same kernel for both the host and the guest systems. The phrase "glorified chroot" comes to mind, though I'm aware that it's more than that (just adding it for the sake of trolling, I guess :-)). Xen, VMware and QEMU/KVM are, on the other hand, real virtualization solutions, where all the virtual system runs completely isolated.

        I wouldn't recommend Xen for home use (VMware Server is a better and easier option, IMHO), but saying that it's not ready and comparing it to QEMU/KVM is almost a joke.
      • Re:Stop the press (Score:4, Informative)

        by jaseuk (217780) on Tuesday May 15, 2007 @05:32AM (#19127749) Homepage
        Virtuozzo/OpenVZ and VMWare have strengths in completely different areas.

        VMWARE is an excellent DR/BC solution due to complete virtual machine portability. However consolidation ratios (8:1 maybe) and performance are not that great, for consolidation you've probably only saved a few Us, but you have not really helped reduce the support burden, you'll still need lots of middleware / server management software to manage your estate. To actually get the most out of the DR/BC solution you also need an FC SAN and the complete Virtual Centre suite. If you've that kind of money to throw around then clearly you are in it for BC/DR purposes and VMWare is the right option. At this level you don't care if your consolidation ratios are 1:0.9 or worse.

        Virtuozzo/VZ on the other hand wins hands down for consolidation and management; you can easily fit 20-30 or more VPSes on a single server; and whatever the consolidation ratio the responsiveness will always be better than the same server under VMWare. However there are some drawbacks, Virtuozzo doesn't give you complete portability; you can only host Windows 2003 guest servers on a Windows 2003 hardware node for instance and you are unable to install device drivers. Adding a new VPS takes about as long and uses about as much resource as creating a new user on a system.

        I use both solutions; each definitely have their own place and couldn't be more different in their relative strengths.

        Jason
        • by birder (61402)
          I'm running several VMware ESX servers (4 CPU Opteron) with 15-20 VMs each and they're not even loaded up yet. I even have a ancient 4CPU Dell box running 16 VM's smoothly. Certain applications aren't VM friendly but 90% of them are and it is a great savings in power and space. VMotion is awsome as well not just for DR but for regular maintenance. When you have 15+ servers running on one box, it's hard to schedule ESX downtime to make everyone happy. VMotion solves this for us.
          • Re: (Score:3, Informative)

            by jaseuk (217780)
            VMWARE consolidation tends to be limited by your overall system RAM. I can only assume that you are making very small RAM allocations (128M-192M?) or you have a large amount of physical RAM available (12-16GB?)

            Jason.
            • by Ryan Amos (16972)
              I'll second this... Also, responsiveness starts to severely bog down when you have 8-10 VM instances on a box; I use it for testing AJAX web applications and we really can't rely on it for speed because the latency gets pretty bad at that level. I've used Virtuozzo's commercial product in the past, and you can indeed cram ridiculous numbers of VMs per box. We had modest Dell rackmount servers hosting 80-150 VMs and response times were still decent. The migration tools available on their commercial product a
        • The bigger issue with VMWare is licensing costs.

          Unless you're spending $20k-$50k per server on hardware, VMWare pricing will seem very expensive (in the $3-$4k range per server is what I was quoted a few months ago). For smaller shops that have a few $6k-$10k servers and a small SAN, the VMWare costs make it a very hard sell (almost better to order another server).

      • As somebody that has used OpenVZ, VMware (several flavors, since the early beta days), QEMU, Bochs, Linux-VServer, and others, I like OpenVZ (and VMware Server but for totally different reasons). I looked at Xen and decided that I would grow old setting it up, so I abandoned that effort, for now.

        OpenVZ is easy to setup (once you get the kernel and packages setup, which is a breeze in Debian 3.1 and 4.0). It runs ridiculously fast, it consumes little memory, and takes little disk space (which can be furthe
      • Yeah but Xen is still a royal PITA to get running.

        If you think that Xen is a "royal PITA" to get running, then how do you manage to work with a server? There is a slight learning curve, but after that it's extremely easy to deal with. Much like most Unix things. The massive performance benefit that Xen gives over VMWare Server (the only one I use) is well worth the hour it takes to learn the basics.

        Now, if you're virtualizing a desktop system, VMWare rocks. I use it daily for this. But after using both in production, Xen clearly has a significant perf

        • by drsmithy (35869)

          If you think that Xen is a "royal PITA" to get running, then how do you manage to work with a server?

          Most likely, he's trying to do non-trivial things with Xen. Stuff like bridges to multiple vlans, interface bonding, multiple drives, and the like.

          Xen *sucks* from an administrative perspective if your environment is anything remotely complicated. VMWare has nothing to fear.

          There is a slight learning curve, but after that it's extremely easy to deal with. Much like most Unix things. The massive perfor

      • OK what you're missing here is that there are two sides of virtualization (well technically there are more but we'll go with 2):

        OS-based virtualization, which is done by OpenVZ, is based on "Virtual Environments" that all run under one kernel. It's kinda sorta like running different servers in their own "chroot jail", but with their own virtual interfaces, their own quotas, etc. etc. Generally because you're not semi-emulating hardware paravirtualization is faster

        Para-virtualization, which is done by Xen, K
      • The FC6 Xen configuration was downright easy. Reboot into Xen kernel, run virt-manager, type in the URL for the install image, pick a virtual hard drive file/partition/lv, specify an amount of ram and number of CPUs and click finish.

        Repeat.

        Granted, I only used it for installing other FC6 images, but it was very simple.
      • it will take some time for Xen to be considered out of the hobbyist market
        If you consider Amazon to be a hobbyist... Amazon launches Xen-powered virtual datacenter on demand [virtualization.info] or Amazon Elastic Compute Cloud (Amazon EC2) [amazon.com]
    • by ovz_kir (946783)
      Let me answer this way: Show me a single exploitable security hole in OpenVZ, or the way for a VE to do a Denial-of-Service for other VEs (i.e. the case of improper isolation) -- when we'll talk.
    • by ppadala (220707)
      > No kidding, that's why I use it! Xen's performance ain't so bad.
      > Show me a better performing virtualization solution that matches or bests Xen's isolation security - then we'll talk.

      KVM [qumranet.com] ? Though it is in early stages of development, in theory, it may be able to run faster than Xen. It's goals, however are different from that of Xen's
  • KVM (Score:2, Insightful)

    by QueePWNzor (1044224)
    Kernel VM is based off QEMU -- but doesn't Xen have a similar hypervised Linux kernel. (I personally thought that may be why KVM was created -- to be a better Xen.) As I'll eventually upgrade to a Linux distro with KVM, I wonder if there are similarities in them -- or preferably if KVM could be fully tested and compared with these results.
  • by fred911 (83970) on Monday May 14, 2007 @08:54PM (#19124725)
    " hypervisor-level virtualization technology that allows multiple operating systems to be run with and without para-virtualization "

      I don't know about you but it still makes my eyes hurt!
    • by interiot (50685) on Monday May 14, 2007 @09:07PM (#19124845) Homepage

      Hypervisor [wikipedia.org] — the software that makes the virtualization happen... sometimes means virtualization that runs on bare-metal, rather than under a host OS.

      Paravirtualization [wikipedia.org] — I think this just refers to the cases where the guest OS is modified/recompiled to run work without needing to run in Ring 0, and instead changes those to be explicit calls to the virtualization software.

      So translated, I think that means "virtualization software that runs on bare-metal, both using unmodified guest OS's, and modified guest OS's."

      • Re: (Score:3, Insightful)

        by Jartan (219704)
        From reading the article on hypervisor it still seems ambiguous. It implies that a hypervisor is not exactly a VM but the actual detailed description makes it out to be a VM. Others seem to imply it means the VM is running as an OS basically.

        From everything I can see though the word is useless and it amounts to the equivalent of computer scientists being fussy. VM or VM OS are better choices.
    • by Tumbleweed (3706) *
      " hypervisor-level virtualization technology that allows multiple operating systems to be run with and without para-virtualization "

      > I don't know about you but it still makes my eyes hurt!

      Really, it's not that complex. The technology monitors all system calls, and makes a judgement call - if it's safe to let it through, it routes it through the EPS conduits. If it's not, it routes it through the GNDN tubes. As long as you don't overload the EPS taps, it's all good.
  • by jd (1658) <imipakNO@SPAMyahoo.com> on Monday May 14, 2007 @08:58PM (#19124749) Homepage Journal
    how big a performance penalty Zen pays

    Zen's performance issues were fixed by Avon, under Orac's guidance.

  • vserver + unionfs (Score:1, Informative)

    by a1mint (1021941)
    I use vserver in combination with unionfs, which just rocks.

    I can add and remove (semi) virtual machine at will. Each VM feels barely heavier than just an ordinary process.

    I take my normal mount points, and make it the read-only layer. I then add a writable layer on top of that and that's it. I've also created some handy scripts that'll let me manage, add, remove, start, stop, etc, VM's.

  • by Anonymous Coward
    OpenVZ works with FreeBSD?

    Does anyone have links to show the support?
    • by tres (151637)

      OpenVZ and Virtuozzo rely upon Linux kernel modifications; in other words, no FreeBSD, no Windows.

  • Both are good. (Score:5, Informative)

    by Blackknight (25168) on Monday May 14, 2007 @09:30PM (#19125023) Homepage
    As somebody that actually has experience setting up and running virtualized systems (I work for a web hosting company) let me add my two cents here.

    OpenVZ is ok if all of your child environments run the same OS and you don't care about them stealing each other's resources. We constantly have problems with customers overloading their VPS and causing problems with the other environments, this doesn't happen with Xen. I've fork bombed child environments and caused the load to spike to over 700 until it crashed, dom0 and the rest of my domUs just kept running like nothing was even happening.

    OpenVZ also wins if you want to oversell hardware, Xen doesn't have "burstable" memory like OpenVZ does. Personally I prefer Xen for the jailing that it does and you can also run multiple OSes at the same time. I have a server at work that's running CentOS, Windows 2003, Windows Longhorn, and Gentoo all at the same time, OpenVZ only lets you run Linux on Linux.
    • Re:Both are good. (Score:5, Informative)

      by flydpnkrtn (114575) on Monday May 14, 2007 @10:27PM (#19125415)
      When you sit down and do your homework, and don't oversell as you said, OpenVZ gets the job done. I was looking for a good way of virtualizing a new server we were moving to and I've gotta say I can't see myself ever NOT installing a server in either an OpenVZ VE or a Xen domU ever again.... with OpenVZ you can give one VE (almost) all the resources of the hardware its running on, and when that one server outgrows that hardware doing a vzdump or vzmigrate is sooo easy.

      The big difference between Xen and OpenVZ comes down to what openvz calls "privvmpages" - memory that is claimed by running processes but not actually used.

      The example here is this: two OpenVZ virtual environments (VE) can be set up on a server with, say, 1 gig of ram, with a gig of swap underneath it (So, RAM+Swap equals 2 gigs).

      Those two virtual environments can be "oversold" in the amount of privvmpages they're allowed to use, because processes ask for more memory than they _actually use_ all the time. So let's say we give those two VEs 1.5 gigs of privvmpages (total of 3 gigs - more than RAM+Swap), but we only give them each 500 megs of oomguarpages. (less than RAM+Swap).

      The thing that _should never_ go over RAM+Swap is oomguarpages (out of memory guaranteed pages) - pages of memory that are guaranteed (OpenVZ measures some of its resources in pages and some in megs).

      With Xen, on that server I just described you're locked in - there's no bursting, and there's no dynamic allocation going on. You give one domU 750 megs of ram and you give the other domU 750. That's it.
      • Re: (Score:3, Insightful)

        I've gotta say I can't see myself ever NOT installing a server in either an OpenVZ VE or a Xen domU ever again

        Remind me to never EVER hire you to do any work for me. Ever heard of "the right tool for the job"? I am a huge fan of virtualisation, and have been using it for years, VMWare mostly, but lately more and more with Xen. Given that Xen simply does not yet play nice with most of the lower cost hardware, and has several significant shortcomings in real-life enterprise production environments (running
        • Saying you will only ever use virtualised workloads is stupid, and unprofessional. -and no, the fact that you got [oracle,mysql,postgresql] to run in a VM does not mean its going to be anywhere near decent performance.

          I wasn't specifically saying I would do the virtualization with Xen... if it was specifically a Linux server I would most definitely run it in an OpenVZ VE. You seem to think "virtualization" automatically means paravirtualization, not OS-based virtualization.

          What I meant was that even
          • You don't have to sell me on the benefits of virtualisation. I'm all for it. None of the benefits you list are exclusive to virtualisation. If on the fly snapshotting is a key business requirement for me, I will pick the right tool for the job. Depending on the customer (well, mine anyway) that will usually be a more specialised storage device. I can go on and on, but the bottom line, the attitude that you will "NEVER" use anything other then virtualisation is unsound
    • by ovz_kir (946783)

      OpenVZ is ok if all of your child environments run the same OS and you don't care about them stealing each other's resources.

      OpenVZ isolates VEs from each other pretty good, unless you misconfigure it. The problem here is you can't configure the system properly (i.e. you oversell way too much). See this article [openvz.org] to get the details on how to configure your system in a proper manner.

      • by Tony Hoyle (11698)
        The worst virtualisation experience I ever had was on Virtuozzo. I was with a host that was running UML. Everything worked fine, no issues with it.

        Logged in one day and nothing worked. The host had changed to Virtuozzo. They tried to sell us on the advantages 'look it has a cool web based frontend' they said. It sucked. It had lower bandwidth, lower memory available and was as slow as molasses (like the load average never went below 4 on an idle system running nothing else).

        We coped with that for abou
        • by ovz_kir (946783)
          See what the problem is -- a provider can oversell, and they oversell, sometimes way too aggressively. As long as you are not the owner of a physical server, you can not do anything about it but buy from more sane provider. This has nothing to do with the technology itself. As for technology, see the HP labs evaluation.
          • Just because a lumberjack doesn't know how to use his tools properly, don't blame the chainsaw because it ran out of oil and seized up

            Thnaks for OpenVZ btw! It's a great product, when used correctly

    • by Cyberax (705495)
      OpenVZ allows you to set CPU and RAM quotas, and in my experience they work just fine.

      OpenVZ also has a very distinct advantage - all processes in guest VEs are visible to the tools on the main host.
  • by Anonymous Coward on Monday May 14, 2007 @09:52PM (#19125195)
    Does it run multiple instances of Linux?
  • And... (Score:5, Insightful)

    by coyote4til7 (189857) on Monday May 14, 2007 @10:16PM (#19125347) Homepage
    Nothing like a virtualization comparison that ignores the 800 guerilla that is VMWare. How do the learning curves, performance and security of these products compare with VMWare? Why should someone who is satisfied with VMWare consider other alternatives?
    • Re: (Score:3, Interesting)

      by myowntrueself (607117)
      Why should someone who is satisfied with VMWare consider other alternatives?

      How should someone who is satisfied witn VMWare decide whether an alternative would be an improvement? When the license terms for VMWare prohibit any benchmarking its kind of hard to make a decision.
    • by Anonymous Coward on Monday May 14, 2007 @10:41PM (#19125517)
      Here are a few talking points based on my experiences with both Xen and VMWare (ESX Server & Workstation).

      1. Cost - no contest, xen wins hands down $0 vs $5000/cpu.
      2. Performance - xen wins noticably, i can get away with running 8 virtual machines with 1/4 the hardware that VMWare required for 6.
      3. Capabilities - VMware versions ESX GSX and up beat Xen in ease of use and flexibility, anything less and Xen wins. Xen does have a quicker live migration capability, but falls short on conencting external hardware to the virtual machine (something that is trivial in VMware).
      4. Stability - about even, maybe Xen. I've seen ESX crash once, and have never seen Xen crash.
      5. Ease of use - VMWare no question. Theres a learning curve to Xen and setting up new VM images is a pain. (which is disappearing) There are fantastic tools for VMware that will let you manage virtual machine creation and even migration from a physical box. (some of which can be used to feed xen too =))

      The bottom line. A Xen setup (using open source version) that can easily run 12 VMs costs about $2,000 on DIY hardware. A VMWare server/software combo to do the same? about $30,000. Assume an additional 40-80 hours of learning to get up to speed with Xen vs VMware.

      The comments above cover the open source / free version of Xen. I have no experience with the commercial Xen offerings.

      Personally i'm Xen biased due to cost.
      • by eht (8912)
        And I'm biased to VMWare for the exact same reason, I think someone may be underpaying you.
      • Re: (Score:3, Insightful)

        by Xouba (456926)

        Personally i'm Xen biased due to cost.

        I agree. Just a little addition: besides, VMware licenses are even more important when you want to scale. Say you want to use two quad boxes for load balancing, running VMware in each: that's about 8 x 5000 = $40000 in licenses (or $35000 if the first CPU is for free; I'm using your prices, but I knew about a similar project where VMware was decided against due to licensing costs too). You can buy more hardware with that money and train all your staff to understand

      • by mbourgon (186257)
        2. Performance - xen wins noticably, i can get away with running 8 virtual machines with 1/4 the hardware that VMWare required for 6.

        Tell me more, please. Looking at the Xen performance paper, it looks like Xen & VMWare are pretty close, performance-wise. The most they ever show is a 23% boost on a couple tests - nowhere near the "1/4 the hardware". Not trying to bait, but honestly curious.
      • Re: (Score:2, Insightful)

        by phish (46788)


        There's one item you didnt list, though it might be folded under capabilities or ease of use...

        Manageability is a key item for these types of setups. As people being to depend more and more on virtualization technologies (whatever those might be) and roll out virtualized production environments, you have to figure out how to monitor and manage them. This is one area where VMWare currently has the upper hand, as Xen's management API has not yet been stabilized.

        The reason this is important is because with all
      • Re: (Score:3, Insightful)

        by Thumper_SVX (239525)
        You missed the biggest point for a corporation; Support. No corporation looking at virtualization (and let's get real; almost all of them are) is going to use Xen OR OpenVZ at this point because there's no single point of contact for support, and no support contracts.

        Quite simply, a corporation is going to buy VMWare Virtual Infrastructure. So the performance isn't as good? So what? Throw hardware at it. It works.

        We have a significant investment in VMWare VI3 where I work, and it's great. We run it on high-
        • by Macka (9388)

          You missed the biggest point for a corporation; Support. No corporation looking at virtualization (and let's get real; almost all of them are) is going to use Xen OR OpenVZ at this point because there's no single point of contact for support, and no support contracts

          Um, what about Redhat and Novel (SuSE)? Redhat have restructured how they sell RHEL 5 based exclusively on how many Xen VMs you're allowed run. Their standard RHEL 5 Server allows you to run up to 4 guest VMs, where as RHEL 5 Advanced Platf

          • Um, what about Redhat and Novel (SuSE)? Redhat have restructured how they sell RHEL 5 based exclusively on how many Xen VMs you're allowed run. Their standard RHEL 5 Server allows you to run up to 4 guest VMs, where as RHEL 5 Advanced Platform allows an unlimited number of guest VMs and also includes the RHEL Cluster suite. If the guest VMs are RHEL then it's all included in the one cost, and of cause it's fully supported. There's no excuse for turning your back on Xen based on support.

            And who does one turn to when a bug is found in the code? One that is critical for your functionality?

            Don't underestimate this as a driving factor for corporations. We had this exact problem with the first release of VI3, and it was a show-stopper bug. We called EMC, and had a significant patch sent out to us within 48 hours which was subsequently rolled up into the next release. The problem corporations see with Xen and OpenVZ is that there are no programmers at the companies you mentioned actually coding

      • by darrylo (97569)

        Going off on a slight tangent, VMware Workstation (non-free, $$) is the only one that has a glimmer of (imperfect) DirectX support, although there are rumors about similar support in the forthcoming OS X version. This is important for home users (not enterprise or business users) that run windows to play real-time 3D games. ;-)

    • Re:And... (Score:4, Informative)

      by Chirs (87576) on Tuesday May 15, 2007 @12:35AM (#19126363)

      This is a bit out of date, but here is some comparison between Xen, User Mode Linux, and Vmware 3.2 (which is the most recent version that allows publication of benchmarks).

      http://www.cl.cam.ac.uk/research/srg/netos/xen/per formance.html [cam.ac.uk]

      Xen is always faster than Vmware, with the exact amount varying depending on the specific load. They've all improved since then, of course.
    • by soulhuntre (52742)
      Microsoft's Virtual Server is a free product now and does a really, really good job.
    • by ppadala (220707)

      Nothing like a virtualization comparison that ignores the 800 guerilla that is VMWare. How do the learning curves, performance and security of these products compare with VMWare? Why should someone who is satisfied with VMWare consider other alternatives?

      We would gladly run the same kind of experiments on VMware, but VMware does not allow publishing results, unless they have a look at them first. They probably don't want unfavourable results to be published. As an academic, I really hate such restrictions and want to do an un-biased study.

      Pradeep (Primary author of the mentioned report)

  • Other VM options.. (Score:3, Informative)

    by tji (74570) on Monday May 14, 2007 @10:42PM (#19125531)
    Linux has a lot of great VM options. VMware is a great free (cost) option, and KVM has become a great option very quickly. OpenVZ and VServer are interesting light weight OS "jail" virtualizations. They each have pros and cons, depending on your requirements and apps being used.

    I'm setting up my "next generation" home linux server, and looking into the virtualization options for that. Probably a bigger factor than performance is the setup and manageability. I have found Xen to be pretty primitive compared to VMWare.. setup is a pain, documentation is spotty, and support is minimal. The one advantage of Xen is that you can (and often must) do everything with it from the command-line. The GUI tools are weak at best.

    I am now leaning towards using VMWare server. But, I still need to do some testing with KVM.. articles I have read about it sound very impressive. KVM paravirtualization performance is supposed to be excellent. But, I don't know about management.
    • I have found Xen to be pretty primitive compared to VMWare.. setup is a pain

      That's what I thought, too. Until I installed CentOS [centos.org] (*the* RedHat Advanced Server clone). Start virt-manager, click Create, click next-next-finish and voila, you have a window showing an installation.
  • by MavEtJu (241979) <<gro.ujtevam> <ta> <todhsals>> on Monday May 14, 2007 @10:54PM (#19125627) Homepage
    Go the FreeBSD way!

    Lousy virtualization, Happy users: FreeBSD's jail(2) facility [ukuug.org]
    Source: UKUUG [ukuug.org]
    Tags: ukuug, presentation, freebsd, jails, poul-henning kamp
    Slides (2.7 Mb) [ukuug.org]
    Lousy virtualization, Happy users: FreeBSD's jail(2) facility by Poul-Henning Kamp (phk@FreeBSD.org)
  • by cerberusss (660701) on Monday May 14, 2007 @11:54PM (#19126077) Homepage Journal
    It's not always about performance; Xen gets each their separate kernel. This means that special adjustments can be made for a virtual machine. Also, with Xen you could easily experiment with an upgraded kernel for the virtual machines, without rebooting the main (host) machine. Finally, I for myself like the fact that you have your 'own' kernel. It feels much more like a real machine. Especially with a bootloader like pygrub, which is employed in RedHat AS and CentOS, the kernel inside the virtual machine can even be upgraded by yum running inside the VM.

    Note that I'm not a Xen apologist, I'm not denying a performance hit here.
  • by flyingfsck (986395) on Tuesday May 15, 2007 @12:31AM (#19126335)
    OpenVZ is somewhat like FreeBSD Jails. It provides some separation which makes it easier to manage multiple complex servers. For example, it makes sense to run a web server and mail server in two separate virtual machines, since it keeps the configuration independent.

    Xen, is like VmWare or Qemu and provides an independent virtual machine for each system. These systems can be anything at all: Windows, Linux, BSD, whatever.

    Performance wise, OpenVZ is bound to win, because it is a different solution to a different problem.
  • As long as the performance is not bad, I'll take isolation and ease of use over an edge in performance any day. If performance is not good enough, I'll buy a faster server. If the virtuals start disturbing each other, you won't be able to fix it easily and it might be very expensive on the long run.

    I have to admit I don't have a lot of experience with Xen, and even less with OpenVZ. If I was building a server at home I would probably use Xen as it's free. At work I'm happy with VMWare ESX 3. Might be the

    • I'm not that impressed with the free VMWare Server. While it works in most things, it has very bad disk IO performance Same goes for Xen, if you use simple files as a backend. I suggest you create separate partitions for VMs. If that's not flexible enough, create a huge LVM partition [wikipedia.org] and slice it in pieces for VMs.
    • Re: (Score:2, Informative)

      by ovz_kir (946783)

      In fact, free OpenVZ has most of what you tell about VMware. Live migration is here, and it does not require to have a SAN or a dedicated NIC, or pay for vmotion. High availability with clustering can be set up (see here). And finally, you don't have to pay a performance penalty if you want virtualization.

      The commercial product based on OpenVZ (i.e. Virtuozzo) has all that plus web-based and gui management tools, P2V migration tools etc. etc.

      It also makes sense to point out that Xen also has a live migr

  • Hypervisor for both (Score:2, Interesting)

    by gokalp (686689)
    We're using HyperVM from LxLabs http://www.lxlabs.com/ [lxlabs.com] and it manages both OpenVZ and XEN. You can easily watch the performance penalties of both virtual machines from the same panel and migrate in between. So whenever someone abuses OpenVZ you can migrate it to XEN.
  • I used to have a Virtuozzo server, but after I started noticing poor PHP performance, my hosts migrated to a Xen3 machine and I must say the speed *increase* was quite impressive, and that was running with less physical RAM allocated, and more swap, on the same spec Opteron box.

    So maybe OpenVZ has some improvements over the commercial variant (seems backwards) or the article is talking about an old Xen2?

    I'm currently moving onto a real hardware colo system, which is more hassle, but gives me more control.
    • by ovz_kir (946783)

      my hosts migrated to a Xen3 machine and I must say the speed *increase* was quite impressive

      This probably relates to the fact that people usually run 5-20 Xen guests and 50-200 OpenVZ VEs on the same box.

      that was running with less physical RAM allocated, and more swap

      In OpenVZ, you should not take a look at what free or cat /proc/meminfo shows you -- instead you have to take a look into /proc/user_beancounters to see how much RAM etc. you have.

  • by ovz_kir (946783) on Tuesday May 15, 2007 @06:52AM (#19128173) Homepage

    Xen trades off performance for much better isolation and security.

    I guess I have to correct you here. Xen trades off performance for an ability to run different kernels, and this has nothing to do with either isolation or security. So, Xen is good when you want to run different kernels (different OSs).

    OpenVZ, on the other hand, employs a single kernel model, which makes it suitable for you if you only want to run Linux (different distros are possible, different kernels are not). But in this very field OpenVZ is way better than Xen -- not only in terms of performance, but also scalability, manageability, density, and usability.

    Speaking of isolation and security, OpenVZ runs on thousands of ISP/HSP servers, and everyone can buy a VE (Virtual Environment) for about 10-15 bucks a month. There one have a root account and can try to exploit the system in all the possible ways. So far those HSPs are not out of business yet, that practically proves the system is secure and properly isolated. More to say, security comes from the constant care, and we (OpenVZ team) do care for security a lot, see this blog entry [openvz.org] for some more details.

The confusion of a staff member is measured by the length of his memos. -- New York Times, Jan. 20, 1981

Working...