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OS Virtualization Interview

Posted by ScuttleMonkey on Tue Apr 18, 2006 08:37 PM
from the new-distro-smell dept.
Software Linux
VirtualizationBuff writes "KernelTrap has a fascinating interview with Andrey Savochkin, the lead developer of the OpenVZ server virtualization project. In the interview Savochkin goes into great detail about how virtualization works, and why OpenVZ outshines the competition, comparing it to VServer, Xen and User Mode Linux. Regarding virtualization, Savochkin describes it as the next big step, 'comparable with the step between single-user and multi-user systems.' Savochkin is now focused on getting OpenVZ merged into the mainline Linux kernel."
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[+] OpenVZ Pushing for Linux Kernel Inclusion 160 comments
RomanianClimber writes to tell us News.com is reporting that SWSoft is trying to get OpenVZ into the Linux kernel. OpenVZ is an operating system level server virtualization solution, built on Linux. From the article: "In this, it has a major ally: Red Hat, the top seller of the open-source operating system, which plans to add the software to its free Fedora version of Linux for enthusiasts. The companies' move to make OpenVZ partitioning standard in Linux is timely, said Pund-IT analyst Charles King."
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  • ...that virtualisation is going to be that much of a Big Thing(tm). Those that will get the most use out of it will be the would-be dual/tri/mega-booters, and, let's face it, compared to the number of computer users in the world - heck, to the number of people that know roughly what virtualisation is - that number is going to be quite small.
    • well isn't Linux used mostly for server operations? Virtualization also adds a layer of safety and security between child OSes and their processor.
      • I don't see why such a layer is necessary, or what it will ultimately provide. The OS is supposed to protect users and apps from each other! If virtualization becomes widespread, it will have to take on more and more of the roles of an OS until it *is* an OS. For instance, an OS has a bunch of logic (a scheduler) to grant processes "fair" access to the CPU. With virtualization, you need another scheduler to schedule among the schedulers!!
        • Exactly. something to sit above the kernel, or "supervisor"... something like a "hypervisor", which is exactly what xen's marketing department wants us to call the xen kernel
        • actually, the virtualization software or the 'host OS' itself handles the scheduling. in server farms quite often the virtualization software runs 'bare metal' (eg: the system boots straight into the virtualization software, and loads any images etc.) but most geeks run it on top of a full fledged Os where the software can rely on any built in shcedulers etc. I have noticed that certain devices (soundcards, for example) don't always play nicely with being shared, but others (LAN cards) handle being shared v

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

          by Anonymous Coward on Tuesday April 18 2006, @10:35PM (#15154745)
          A virtual server can be restored in seconds, no rebuild required. A virtual server can be moved to another host server in seconds without ever shutting down. A virtual server has a common hardware configuration and can be moved to another host with completely different physical hardware in seconds without shutting down (you can mix Dell and HP servers for example and switch between them on the fly). Not every virtual server needs dual Xeon processors and 8GB of memory, but a bunch of virtual servers can run on that machine and share load as required and if one of those virtual machines needs a little extra umph for some biweekly processing, it has the ability to grab more resources or the other virtual servers can be moved off to another physical server hosting virtual servers with more power without ever shutting it off [1]. Redundancy in the virtualization world requires two physical host servers each able to carry the load of all the virtual servers and a shared disk area (SAN, iSCSI). To have that level of redundancy in the plain of non virtual world, each server would have to have a second physical server for backup and unless you were clustering, you would not have the ability to move over your processes to the backup physical without some type of interuption if one of them suddenly failed like in your example.

          Virtualization has many advantages in the enterprise and the ability to recover from a virus in your example is one small part of the whole package.

          [1] Host servers can share memory between virtual servers, not just the total memory but the memory between machines as well. Very simple example but if you open sol.exe on one of the virtual servers, you will not take up any more total memory on the host machine by opening sol.exe on another virtual server on that same host. The memory is shared between the running virtuals as well. This works great when you have quite a few of the same OS being virtualized on a host. You could run 10 plain vanilia virtual copies of Windows server 2003 and the total memory taken up on the host will be less then 1.5 times more then a single running copy of that OS, not 10x of a single virtual. That example of 10 exact copies is not likely in real life but the common memory is shared which can make up for a significant amount of total memory savings.

          Don't let your lack of insight or knowledge of the capabilities of virtualization get in the way of your opinions ;)

    • Re:I'm not convinced... (Score:5, Insightful)

      by Abcd1234 (188840) on Tuesday April 18 2006, @08:59PM (#15154396) Homepage
      Uhh... these products aren't aimed at your desktop box. They're for use in server farms, where virtualization provides an additional measure of security, along with providing the server operator more flexibility in how their hardware is utilized.
      • That's true, but come on, it's going to be pretty fun to play with on desktop machines, too, isn't it? Imagine all the tricks you can play on computer-illiterate friends/family. One second it's Windows, the next it's MacOSX, then 10 seconds later it's Linux! Heads may explode.
      • Uhh... these products aren't aimed at your desktop box. They're for use in server farms, where virtualization provides an additional measure of security

        If windows apps (or group of apps) were virtualized, we could use activex webpages without having to worry about spyware. Just close the virtualization window and it's gone.

        The same for e-mail, if you restrict write access only to the mail files, and all spawned process from the e-mail were virtualized. If it screws up, the most you lose is your e-mail, but
        • That's brilliant, instead of actually expecting secure software, let's just use a 40 pound sledge to drive a nail. Virtualization means running a nested kernel, I don't feel like booting a sub-OS everytime I want to check mail or open a browser. It's far more efficient to just write the app properly.

          I guess the true question is: Which solution is more likely to get attention ? Whiz-bang virtualization will probably win, since it seems very few people in this world have the patience and discipline to writ

    • Re:I'm not convinced... (Score:5, Insightful)

      by NitsujTPU (19263) on Tuesday April 18 2006, @09:02PM (#15154408)
      Nah nah nah. It's going to be great. Picture this. You manage a university computer lab. The computers all have identical software, and all of the students files are stored on a network share. When computers are not in use, you'd like to dedicate the cycles to a long-standing distributed computation for experiments carried out by one of the departments.

      The student logs in and a disk image runs their OS of choice, they don't have to reboot or know much, they just click an icon saying which OS, which instantly is presented to them. A batch process manager removes the load from the distributed experiment from their machine.

      Or, perhaps something that's already fielded. You're a graduate student, and want to emulate 1000 compute nodes for a distributed computing experiment, you log into emulab, and tell the 50 that you've signed up for to boot 20 OS's a piece, and emulate a 1000 node network.

      Or, perhaps you're studying viruses (this has also been done), and want to build an Internet scale honeynet.

      Or, perhaps you're running a large server farm. You want an easy way to load balance a multitude of services, so you can run something that looks like 100 servers on perhaps 50. By dynamically balancing across nodes, services can automatically adjust themselves, independently of mechanisms built into their software (to some degree). When you want to add new hardware to the network, you just plug in the machine, and tasks start being farmed to it. When you want to retire some, you just tell the manager to stop moving tasks onto that machine, and wait for the tasks on that machine to move off.

      Briefly put, VMMs rock. You have to think outside of "geeks playing with VMWare" to really see the interesting applications though.
      • Thanks for the post, it gives me some insight into what virtualization is. But I'm still confused about what it actually does. I read this entry over on wikipedia:

        http://en.wikipedia.org/wiki/Virtualization [wikipedia.org]

        Does virtualization basically run multiple OSes on one box? Make one computer appear to be 2, or 3, or n?

        Steve

        • Yep (Score:3, Informative)

          by XanC (644172)
          That's basically the idea. A single machine can be running several different systems at once, and each one can have its own kernel, network settings, tuning for a particular task, whatever. You can set up the network however you want; you can even simulate subnets and routers and who knows what to try stuff out.

          Another big advantage is that the virtualization provides a common "hardware" layer. For example, every VMWare "machine" sees standard VMWare "hardware", no matter what kind of metal it's actual

        • In the very simplest case, there is a program called a virtual machine monitor that multiplexes the underlying hardware. Operating systems that run atop this see the hardware as if they have exclusive access to it.

          The cool part comes in what one chooses to do with this. See, now the operating system sets on something that in its simplest sense does this... but one can build more interesting things into the VMM that allow it to do things like snapshot the entire running operating system and move it across
    • I'm not convinced that virtualisation is going to be that much of a Big Thing(tm).

      Allow me to introduce you to the world of Big Business: upper management want the Big Business pay check but, post dot-bomb bubble, they want none of the penalties associated with taking a risk. So you have the "one application per box" mentality. All of a sudden, you've got 20 boxes running at 5 percent utilization.

      Can you see where virtualization would provide "virtually" the same thing with better cost efficiency?

      Make no
    • Virtualization is HUGE. It helps solve a major problem. With few exceptions, most data centers are running out of power, not space. Servers consume 70-90% of their power draw when the CPU(s) is(are) at idle - and most servers in corporate America run below 15% utilization. If I can combine 4-8 servers into 1, I can save a tremendous amount of power. Here's some simple math.
      A server consumes 400 W at idle and 500 W when all 4 processors are pegged at 100% utilization. If I take 4 servers that normally
  • What's with "open" in the name of all these projects. Is anyone really impressed by that anymore?

    Tom

    • Re:OT question (Score:4, Informative)

      by subreality (157447) on Tuesday April 18 2006, @09:10PM (#15154436)
      What's with "open" in the name of all these projects.


      In this case it's an OSS version of a closed-source product called Virtuozzo, commonly abbreviated VZ. I think it's a perfectly descriptive name.
      • Well if it's the closed project it's opened up.

        If it's a clean-house implementation then it's not strictly based on it.

        Call it something else like Vzeeforefree!

        Dunno just annoyed at people abusing the OSS blanket for publicity.

        Tom
      • Bosses don't care if it's open source. They care

        1. How much does it cost to license
        2. How much does it cost to setup
        3. What does it solve any better than what we already have.

        Tom
        • 4. Who can we sue if it breaks
          • Just curious, who do you usually sue when Windows breaks?
            • Good point :)

              I guess the supplier (IBM/HP/Dell whatever) is usually accountable for any breakage that occurs. Failing that, you can call any of the billions of small tech shops that fix Windows installations for enourmous amounts of cash (I used to work for one ;))
              • Ask for support != sue. You can ask your Linux distro vendor for support too. I have yet to see any successful lawsuit over a Windows fault.

  • A bit of bias... (Score:5, Informative)

    by subreality (157447) on Tuesday April 18 2006, @09:05PM (#15154418)
    "why OpenVZ outshines the competition, comparing it to VServer, Xen and User Mode Linux."

    Of course, Andrey works for the software company that wrote this thing, and their closed full-featured flavor, Virtuozzo. The VZ method is a good one, and has excellent performance, but it has its drawbacks, too. Personally, I don't like that my VPSes need to use my VPS provider's kernel, which lacks features I desperately want (like stateful iptables matching), and which forces me to reboot whenever they upgrade their kernel (my VPS can't be migrated to a host running a different kernel), and I can't upgrade until my provider does.

    VServer, Xen, and UML all make different tradeoffs. VZ goes for performance. Saying one outshines the others is just trolling. That's mostly on the part of the /. submitter, but Andrey slants it a little too.

    I don't want to crap on the OpenVZ project. They're working on very cool stuff, and I applaud SWSoft for opening the thing up. I just want people to keep the comparisons in context.
    • You need to move to Linode.com, seriously. They don't have any of the problems you mention. It's all UML for now, although they have some Xen boxes in beta that you can get on.

  • OS virtualization (Score:5, Insightful)

    by Cthefuture (665326) on Tuesday April 18 2006, @09:06PM (#15154424)
    Unlike Xen or VMware this OpenVZ doesn't run a separate kernel for each virtual machine. This seems like a security risk to me. A kernel bug will affect all the running virtual machines. In other words, you only need to break one kernel and you have them all.

    Plus you can't run different operating systems on each virtual machine.

    It does have some positive benefits, it all really depends on what you are doing. I like the security of Xen and VMware better though.
  • The interviewee keeps talking about Xen 3 like it's not out yet, but that's untrue.

    Indeed, Xen 3 has been stable long enough that they're presently at 3.0.2. It's not prerelease anymore, and support for x86_64 and hardware-supported virtualization has been out and about for a while. I have semi-production (used by in-house staff only, but there are folks who can't work if it's down) systems running on Xen3 x86_64 DomUs, and the host they're on has been up (and running unattended) for 117 days now.

    Sun has a OpenSolaris port to Xen (though I think it may be in-house-only still), and I have some good friends working on a microkernel OS targeted at embedded operation with a Xen DomU port pending (such that they -- and people working on it -- will be able to run it in parallel with the OS they use as their development platform). Being able to run more than one kernel -- indeed, more than one operating system -- is a big plus on the Xen side of things.

  • Imagine ... (Score:3, Funny)

    by 3dr (169908) on Tuesday April 18 2006, @09:43PM (#15154559)
    ... a beowulf cluster of virtualization servers running beowulf clusters of VPSes!

  • Its amazing how low utilization of servers is. Developers love lots of servers, but don't use them nearly as much as they say... see article "Virtualization is the COOLEST thing" at http://blog.tallsails.com/ [tallsails.com]

  • Xen misconceptions (Score:3, Informative)

    by jforest1 (966315) on Tuesday April 18 2006, @09:57PM (#15154612)
    Just to clarify: "Using Xen, you need to specify in advance the amount of memory for each virtual machine and create disk device and filesystem for it, and your abilities to change settings later on the fly are very limited." Xen supports a balloon driver that can allows for one to add or take away from the memory allocated to guest operating systems (DomU's). It is highly advised to us LVM2 to allocate disk space for DomUs, since it allows for easy changes to the partition. This makes file system management easier. "But most importantly, OpenVZ has the ability to access files and start from the host system programs inside VPS. It means that a damaged VPS (having lost network access or unbootable) can be easily repaired from the host system, and that a lot of operations related to management, configuring or software upgrade inside VPSs can be easily scripted and executed from the host system. In short, managing Xen virtual machines is like managing separate servers, but managing a group of VPSs on one computer is more like managing a single multi-user server." Using LVM2 as the disk manager as mentioned above, the host operating system (Dom0) can access the DomU's filesystem for troubleshooting and run programs (though it would not be run in the scope of the DomU, I'm not sure that he's actually implying that is the case with OpenVZ). --josh
    • Regarding running applications within the scope of a VE (DomU equivalent), yes he is. I extensively use both Virtuozzo and Xen. Each has their strengths. VZ allows efficient use of memory (shared memory across all VMs) as well as disk space, as binaries _can_ be shared with a copy on write file system. You can do a lot of this in Xen, but you can't mount a Xen domU filesystem in Dom0 when a DomU is using it. In OpenVZ, the filesystem is only mounted in the hardware node and exposed through an FS layer (copy
      • but you can't mount a Xen domU filesystem in Dom0 when a DomU is using it

        Can and do :). Use OCFS2, piece of cake to set up and the because Xen 3.0.2 is based on 2.6.16, it's already in the kernel tree.

        Haven't used it as the root filesystem yet (just as a shared filesystem between domains), but when I do I will (in theory) be able to have 1 filesystem with 'per node symlinks' (ocfs2 calls them something else but that's what they are) so each node/domain can have a separate /etc, /var/run, /var/spool, and so
  • ... and then there's the outstanding IBM p-Series machines with their Hypervisor in
    hardware that benefits from the aforementioned age-old mainframe technology :}

  • I don't doubt that OS-level virtualization is more efficient, but have you ever tried upgrading the OS for hundreds of applications at the same time? It's darned near impossible.

    The great benefit of hardware level virtualization is that you can upgrade one app and one environment at a time. If app-"A" needs Linux 2.4 because that is what Oracle supports - fine, no problem. But if app-"B" needs to upgrade to Linux 2.6 because its reporting suite must have that version, that is ok too.

    It seems to me that OS-l
    • It seems to me that OS-level virtualization is a cool sounding idea that is pretty hopeless in the real world.

      It depends on the application. If you're talking about a web host running lots of web servers it might make sense to use this approach, since the guest systems are likely to be very similar if not the same.
      • I guess if you think hard enough you'll think of a good application for it... but in the case of web server farms, what's the point of having multiple virtual environments unless you are going to open them up to your clients to install their own PHP or postgresql or mysql or whatever darned bit of web technology they want? If all you want is a bunch of web sites on virtual hosts, you can just use the apache virtual hosts function. But if you want to give clients a free for all, you basically have a massive
  • These are not virtual machines. The idea seems to be the same idea behind Solaris 10 Containers, and I wish that had been discussed (pros and cons) in the interview.

    Easier management for vertical stacking of applications on a machine.

    And, yes, it is VERY useful.

    Not for typical home use though. At home, I use VMWare for virtualization, QEMU to run foreign code, and BOCHS to test x86 assembly sequences, all of which I do frequently. Stacking? Not so much, because my main server is a dual PPRO with 128MB -- httpd, imapd, file services, time services, etc. Not a heavy load (104 processes, easy enough to manage manually).

    Ratboy.

  • FreeBSD Jails (Score:3, Interesting)

    by Ragica (552891) on Tuesday April 18 2006, @11:00PM (#15154825) Homepage
    Sounds, once again, a lot like FreeBSD's jail [wikipedia.org] support (which has existed for many years now, and is very stable).

    In what ways is OpenVZ different? I also wonder what their "commercial offering" adds... but i'm too lazy to look.

    I run FreeBSD jails on my box for testing purposes. It's extremely easy to setup and administer, especially with many helper scripts available these days.

    I am loving the simplicity of ezjail [erdgeist.org]. The coolest thing about it (besides the utter simplicity), is that it creates a "base jail" containing an entire FreeBSD install. From there it uses tricks with nullfs to mount parts of that base iinto jail 'instances'... this means each new jail takes only 2 megs of additional space, and about 1 second to create. It also adds security in that the base system remains absolutely read-only, while still permitting customisation and additional software to be installed in the jail.

    I need a new virtual server to test my software:

    ezjail-admin create new-jail-name 192.168.5.123

    Then run the ezjail startup script. And SSH in to my new virtual server. (Note: i set up the default server template to enable SSH and a few default logins... very easy to do. One does not need to use SSH; one can get into the jail environment a few different ways.)

  • History again repeats itself.. (Score:5, Informative)

    by Anonymous Coward on Tuesday April 18 2006, @11:18PM (#15154887)
    In the mid 60's IBM created CP-67 which virtualized the IBM S/360. In the following years the system became VM/370, and has evolved to z/VM today http://www.vm.ibm.com/ [ibm.com]. VM (the general term for z/VM) is made up of two primary components, VM/CP (control program) and VM/CMS (a mini single user operating system). VM/CMS provided the ground work for being able to administer the system, and provided a nice programming environment in that each VM/CMS user had their own "system" that one could edit, compile and run their programs in an interactive environment (think of a MS-DOS type of model -- then remember that this was in the late 60's).

    CMS itself provided some limited simulation of IBM's two other mainframe operating systems OS/360 and DOS. Enough that one could write simple OS or DOS programs and do at least some unit testing. The simulation by CMS was by providing a limited set of the OS and DOS API.

    Unlike MVS or DOS, (or even the CP/M, Windows, or *nix families) VM/CP itself does not provide many services directly. VM/CP does not provide any filesystems, any application APIs, etc. All VM/CP really did was to provide a barebone virtual machine and only provide those services one would find on the bare hardware. It was the responsibilty of the operating system running within the virtual machine to provide the application API, filesystems, application memory management, etc. Communication between vm's were originally only via the raw hardware model (channel-to-channel adapters, shared disk volumes, and a method of "punching" virtual cards and sending the virtual cards to another vm's virtual card reader.) As time progressed, VM/CP did provide some API's that allowed very simple messaging between two vm's (first VMCF - Virtual Machine Communication Facility, and then IUCV - Inter User Communication Vehicle).

    Early on it was "discovered" that the virtual machine model made a lot of sense as a method to implement VM services. For example if one were to look at a modern VM system, you would see that the entire native VM TCP/IP stack is managed within a small collection of vm's. (Under VM/CP, a vm is called a "userid"). The native VM TCP/IP stack consists of a TCPIP userid that manages the network interface devices, and the TELNET server. The FTP userid implements the FTP protocol, etc. Each userid is totally seperate from the rest of the system and from each other (the tcp/ip socket facility "rides" on top of IUCV in a transparent fashion so that a tcp/ip server is coded the same as on *nix).

    Because of the facilities provided by CMS, it is fairly easy to write little servers. For example the orginal LISTSERV server http://www.lsoft.com/products/listserv-history.asp / [lsoft.com] was written as a CMS application. As well as several native VM webservers.

    If one wants to see what is and has been possible in a virtual machine environment, one should at least look at the history of IBM's VM.

    For an excellent history of VM http://www.princeton.edu/~melinda/ [princeton.edu]
    and the VMSHARE archive, an early BBS used by VM system adminshttp://vm.marist.edu/~vmshare/ [marist.edu]

  • And it's coming. But I think VMWare and Xen got it right. OpenVZ tries to do it inside the OS, which makes OS too much more complicated. It's not going to scale.

        • Speaking of complexity, it is indeed complex. Any OS is complex. VMWare itself is very complex. Any stuff that is not trivial is complex.

          The questions are: whether it works, and is it maintainable?

          Whether it works? OpenVZ and Virtuozzo works just fine -- ask anybody who's using it, get a cheap Virtuozzo VPS from one of the HSP, or just install it on your Linux box and see for yourself.

          Is it maintainable? OpenVZ stable kernel is based on Linux kernel 2.6.8 (with tons of backported fixes and driver up

  • It sounds like the *nix VM world is moving along the track established by Multics and IBM's CP/67 (later VM/370) projects.

    It seems to me that the differences in the *nix approaches are mainly whether the abstract machine seen by user written code resembles a hardware machine or some nicer abstract machine.

    In all VM approaches the idea that one can freeze an entire system and look at it, or isolate it, or migrate it, is a very valuable one. It's done well for IBM on their mainframes.

    As for adding resources on the fly - way, way back (mid 1980's) Robin O'Neil and I did a System V based kernel for the Cray's out at Livermore. We had to run on top of the real OS, so we gave each user his/her own copy of Unix and create a file system that could grow or contract, adding, or removing inodes on the fly. And some of those inodes could reference files held by the underlying OS, thus making strange things, like "df" showing less space on the file system than was shown by a "du" summation of the file sizes in the file system. We published a paper on this at one of various Unix gatherings of the time.

    So if we could expand file systems on the fly 20 years ago I don't see why it should be so hard to do today.

    Now if we'd just get serious about capability architectures... (Much of the secure OS work of the '70's was done with capability architectures with hardware support such as the old Plessy machines.)
  • Perhaps I misunderstand virtualization, but this is what came to my mind after reading about it:

    Imagine that in the future nearly every application will be run inside its own private virtual systems. This will be done to improve security, scalability, etc etc. For very complex applications, this will improve the stability of the system as a whole!

    • Price? (Score:3, Insightful)

      by XanC (644172)
      For one. VMWare ESX is quite expensive, I understand.
    • ESX is a lot thicker than openVZ meaning it's emulating a lot more so more overhead. ESX is also more flexable as it run run windows next to lnux next to solaris next to insurt x86 thing here assuming they can deal with it's limited scsi emulated hardware. OpenVZ on the other hand uses one kernel and one filesystem it's one step up from a chrooted jail with a lot of process type limitors similar to ESX. The single filesystem realy keeps drive usage down with a copy on write scheme for the virtuals and you can update all the virtuals at once by altering the base filesystem. OpenVZ was designed for there virtuoso product line thats tageted at hosting companies who have been the big adopters of virtulization as it's a lot safer to sell 1/10th of a 3k server than 10 300 buck "servers" where the 3k box has raid redundant psu's and only takes up one RU vs 10 minitowers taking up nearly a rack and consuming a lot more power with no redundancy.

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