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Disney, DreamWorks, Pixar Go Linux

robinsrowe writes "Most of the major studios use Linux -- such as DreamWorks with more than 1,500 Linux desktops and 3,500 Linux servers. The MovieEditor Conference is an all-day event on computer-based filmmaking in downtown Los Angeles on August 3rd. Studio technology chiefs and other experts discuss ongoing work using Linux in feature animation and visual effects. Presented in collaboration with LinuxMovies.org."

55 of 279 comments (clear)

  1. Jobs on Linux? by __aambat2633 · · Score: 5, Funny

    So Steve Jobs runs Linux now?

    1. Re:Jobs on Linux? by Smurf · · Score: 3, Informative

      They switched to OS X for (most of?) their desktops. Their render farm is still running on Linux.

    2. Re:Jobs on Linux? by hoosrdady · · Score: 2, Interesting

      I got a private tour of Pixar a few years ago right before the move to the new building and at the time most of the artists were using SGI Octane 2 and the Renderfarm was a massive Sun system. About the only Macs I saw where on Steve's desk and a few "office managers" desks

    3. Re:Jobs on Linux? by Anonymous Coward · · Score: 2, Informative
    4. Re:Jobs on Linux? by michaeldot · · Score: 2, Interesting

      Strange, how many years ago? On the documentary extras of various Pixar DVDs, you can see them dotted around.

  2. New Linux Software? by aklix · · Score: 5, Interesting

    I believe I heard that Pixar released much of their software. Even though these are at steep prices, maybe this will give more companies in the same field a chance to switch to linux.

    1. Re:New Linux Software? by Anonymous Coward · · Score: 2, Informative

      If, by "much of their software", you mean prman, and some related tools, then yes, they sell licenses. It is not open source. And, FWIW, this stuff has been running on linux for a few years now, so companies in the field have had plenty of opportunity to switch to linux -- some have been on linux since at least '01, if not earlier (Side Effects' Houdini was the first major 3d app to support Linux).

    2. Re:New Linux Software? by dasdrewid · · Score: 4, Informative

      Pixar writes their own (Marionette, I believe its called), Dreamworks uses Maya and a host of internally developed apps and plugins (for example), but I'd be willing to bet that most of the post-production work is done using Avid or FCP (and of course stuff like AfterEffects), which, for the most part, don't run on linux (Shake does, and it's damn sweet).

      Most smaller companies (commercials, doing stills for magazine ads, and artists) still use commercial products, like Maya, Lightwave, or Animation Master, mostly, I think, for support reasons, but also because, at this stage, they still have features that are missing from Blender (camera/lens types, focal length and depth, and some heirarchy differences). As for cinellera, I don't know many people using it at all (any personally). No one teaches it in film classes, as far as I can tell, and most home users who have the time to mess around with it and understand it either a) also have the money for a cheap mac and use iMovie, which while nowhere as powerful, is good enough for a lot more than you'd expect or b) also have enough time and expertise to get a cracked version of premiere (of FCP if they have a mac) and just use that.

      --
      No trespassing. Violators will be shot. Survivors will be shot again.
  3. So what are the reasons? Cost? Customization? by nweaver · · Score: 4, Interesting

    How much does the selection come down to cost vs customization?

    On one hand, renderfarms of ~5k machines get pretty expensive already, and adding another $500k for windows liscences is no small change.

    On the other, how much of the software is custom/gets customized, and Linux is a better platform for doing custom software and customization?

    --
    Test your net with Netalyzr
  4. studio-linux.org by Anonymous Coward · · Score: 5, Informative

    For an overview of which distros various studios are using (or are migrating to), along with various hardware solutions: http://www.studio-linux.org

  5. So, do we love the studios today? by Anonymous Coward · · Score: 3, Funny

    Lameness filter. :)

  6. WTF? by ErikTheRed · · Score: 2, Informative

    This is just an agenda for a conference. Are they trying to inform us or sell us seats? Is Slashdot getting a percentage? Do editors edit, or chose stories with a randomized function? Inquiring minds want to know!

    Actually, we already know the answer. Never mind.

    --

    Help save the critically endangered Blue Iguana
  7. Re:Apps? by jurt1235 · · Score: 4, Informative

    Look at http://linuxmovies.movieeditor.com/software/index. html The list is what they can possibly use.

    --

    My wife's sketchblog Blob[p]: Gastrono-me
  8. Clusters by andrewman327 · · Score: 3, Informative

    Studios use a lot of clusters, which are much better (in several ways) on Linux than on Windows.

    --
    Information wants a fueled airplane waiting at the hangar and no one gets hurt.
  9. Re:So what are the reasons? Cost? Customization? by jellomizer · · Score: 3, Interesting

    Probably due more to custimization. It is just a lot easier to strip down Linux and make it processes data then it is to do for windows. Being that it is free doesn't hurt. Because they have aready used a good portion on their 5k systems. I find I use linux most at work when I need to make a custom appliance. Get a system powerful enough to do the job I need to be done. Set up linux and usally a small custom app and it just runs. Unlike windows where it just get in the way.

    --
    If something is so important that you feel the need to post it on the internet... It probably isn't that important.
  10. Not just Linux by XxtraLarGe · · Score: 4, Informative

    From TFA: "Get behind-the-scenes Linux and Macintosh insights into feature animation and visual effects production in the motion picture industry." You'll notice that one of the apps they highlight is Apple's Shake, and they mention Mac OS X as a desktop environment with Linux servers.

    --
    Taking guns away from the 99% gives the 1% 100% of the power.
    1. Re:Not just Linux by HyperChicken · · Score: 2, Interesting

      Since they're using Mac OS X, it makes me wonder why they're not using FreeBSD.

      --
      Free of Flash! Free of Flash!
  11. Re:Apps? by Shazow · · Score: 5, Informative

    Here's a good wiki writeup about the available film editing software available on linux:

    Movie Making Manual-Linux in film production

    - shazow

  12. Re:So what are the reasons? Cost? Customization? by Average_Joe_Sixpack · · Score: 5, Informative

    On one hand, renderfarms of ~5k machines get pretty expensive already, and adding another $500k for windows liscences is no small change.

    The choice wasn't Windows vs Linux, it was Linux vs IRIX. This is why SGI's stock is in the toilet.

  13. Rolling Credits by WindBourne · · Score: 2, Insightful

    It would be be nice to see credit given to even some of the OSS that is used in the movies; CineaPaint, Linux (how about a tux), etc. After all, the movie companies want credit when they help on OSS (look at CineaPaint).

    --
    I prefer the "u" in honour as it seems to be missing these days.
    1. Re:Rolling Credits by genooma · · Score: 2, Interesting

      OH COME ON!, just put a little tux in the rolling credits after your movies, that way you are helping the developers of the software you are getting for FREE.

  14. Obligatory American Dad quote by Will2k_is_here · · Score: 3, Funny

    I just touched her hand, and her hand touched her boob. By the transitive property, I just scored!

  15. Re:So what are the reasons? Cost? Customization? by durbnpoisn · · Score: 2, Informative
    I'll tell you what I find really baffling about this...

    I happen to be an amateur filmmaker... No, really... I really am

    I have 3 different Linux machines, of the 5 in my house. But, none of the 3 of them are nearly as practical for all the FX work that I do as my Windows machines.

    And that really sux! I would really prefer to switch to Linux completely... But, the software simply doesn't exist. Unless, of course, you are ILM and have $countless millions$ to afford the top of the line software.

    It's no surprise that these FX houses use Linux. It's been that way for years, in fact. What I would like to see is some of that ingenuity coming down to the home user. It just isn't there yet. And, as a result, I'm still trapped in Windows if I want to get any work done.

  16. not trolling, just a question by rayde · · Score: 3, Informative

    i understand that things like Maya are available for linux, but are there programs out there that are equivalent to say, Final Cut or Adobe Premier... things that an average home movie maker might want?? if Linux is making such big inroads into this area, I'd like to know what apps fill this sector.

    1. Re:not trolling, just a question by TheSync · · Score: 4, Informative

      Check out the open source Cinelerra HD Editor. Also there is a company, Linux Media Arts that specializes in broadcast video solutions with Linux.

    2. Re:not trolling, just a question by lilo_booter · · Score: 2, Interesting

      The jahshaka application is starting to move in the right direction too, in particular for the linux platform.

      The current video editor component is based on heavily on the work of the Kino developers and one of our forays into TV broadcasting. Some more details can be found here.

      There should be a full release of the new jahshaka real soon :-).

    3. Re:not trolling, just a question by shibashaba · · Score: 2, Informative

      Mainconcept, a commerical app is available. One issue with it(don't know if it still exists) is that it wants to load the entire video into memory, so make sure you have a ton of swap space. Cinerralla looks powerful, but I could hardly get it to do anything. Just getting videos into a format it could use was tedious.

      --
      ---------- Open Source is capitalism applied to IP.
  17. Isn't it illegal to play movies on Linux? by jimbro2k · · Score: 4, Funny

    I guess they can create their movies on Linux, they just can't check their work.
    That explains their quality.

    --
    There is not nearly enough love in the world, but there is far too much trust.
  18. Editing or rendering? by stevewz · · Score: 2, Interesting

    As an independent filmmaker and videographer, and as a Mac AND Linux user, I'm curious to see if they use Linux for rendering or editing? There's a huge difference.

    1. Re:Editing or rendering? by NMikkila · · Score: 3, Interesting
  19. Who cares! by aergern · · Score: 4, Interesting

    They can do all these fancy graphics on Linux boxes but this same industry still doesn't support Linux users to view the end product. And when someone takes it upon themselves to do so.. they are taken to court and treated like thieves.

    Screw Hollywood.. they use OSS software but do they give back.. nope. Not really.

    --
    Tell me what you believe...I'll tell you what you should see.
    1. Re:Who cares! by zlogic · · Score: 2, Interesting

      First of all, they don't have to give anything back. It's entirely their choice of doing whatever they want to as long as they don't violate the GPL of whatever license. And second, they DO help the Linux community by making its userbase bigger. Imagine if some company buys software from Pixar and it says "works on Linux only". So using both Linux and Pixar's expertise in using it for film production makes Linux the obvious choice. And also, if some hobbyist/small TV company wants to do video editing, what will they see? Pixar uses Linux, Disney uses Linux, every cool film company uses Linux, so why don't we use Linux? And this scheme works, because when I wanted to move from .NET to PHP I've read an article that GlaxoSmithKline uses .NET and well, I rethought the idea of switching and stayed wit .NET. It's like Pepsi uses celebrities to advertise its products. So why can't Linux use its most popular users for gaining mindshare?

    2. Re:Who cares! by malducin · · Score: 2, Interesting

      It's not exactly the same industry. Most VFX studios work as paid contractors for films. They have nothing to do with the movie studios and media conglomerates. Would you accuse the guy that caters food on the set, or the nurse on set, or the dog trainer for being part of the "evil Hollywood". Movie studios have nothing to do if X or Y VFX studio uses Linux or not, and VFX studios have nothing to do if media conglomarates or software companies release Linux viewers.

      And VFX and animation studios do give something back from time to time (just check around SIGGRAPH). ILM released OpenEXR, FLTK was released by Digital Domain, etc, plus papers they publish. But they use Linux because it's what work best for them. Nothing says they have to release anything is they use it internally (and besides all are trying to have a competitive edge).

      I wonder sine the financial services industry uses a lot of Linux, is there going to be an uproar they are not giving anything back.

  20. Re:Pixar by Dylapoo · · Score: 2, Interesting

    I am not sure if investing in Blue Gene is such a wise idea. Though Pixar does have software running on linux x86 clusters and has experience running off of sparco systems, Pixar is best versed in using their own programs and development systems based upon xserve render platforms. These were the very platforms that were used to render amazingly vivid water scenes in Finding Nemo for less than a million dollars a second (which in the industry is an unheard of level of render efficiency). In fact, the render farm that Pixar used for The Incredibles, known in German as Die Unglaublichen, was an amazing tool in allowing the translation of passive elements of the film into 33 different languages for localized distribution. I discuss on my site here: http://www.dadgev.org/, that the German version of Pixar's The Incredibles actually converted the text in everything from Stock Tickers to Newspaper Articles into German so that the central european audiences would gain as much from the movie as others.

    --
    DAdGeV.org - Top Resource for Immersive German Education
  21. MultiOS by ndansmith · · Score: 4, Funny
    Let me see if I can get this straight . . .

    Movies are made with Linux, feature Apple product placement, and are download on Windows machines? Oh, the beauty of 3!

  22. Irony by EvilMonkeySlayer · · Score: 4, Insightful

    Does anyone else find great irony in this?

    I mean, in order for most Linux users to watch these films they have to break some draconian laws when playing DVD's.

    Yet, the very thing they use to create these films on is Linux.

    Well, if not irony.. some kind of word ending with ony.

    1. Re:Irony by $RANDOMLUSER · · Score: 2, Funny
      > Well, if not irony.. some kind of word ending with ony.

      Um.
      crony?
      morony?
      Ah.
      Balony.

      --
      No folly is more costly than the folly of intolerant idealism. - Winston Churchill
  23. And this is news? by greymond · · Score: 3, Interesting

    Taking a look at the System Requirments for the more well known 3D Animation apps we see Alias's Maya and Softimage's XSI run natively under Linux. Which when you are dealing with animations that can take literally days to render for production it's no wonder they'd want to use a Linux machine instead of a Windows machine, I'm sure it cuts the time by at least 30% (totally grabbed that number out of my ass)

    So is it news that the big animation companies also use OS X instead of XP too? I think the only big name 3d animation company that is Windows only is Discreet with their 3ds Max software, which I think is really only used for games, can't think of a movie that it was used for.

    Sys Requirements:
    http://www.newtek.com/lightwave/requirements.php
    http://www.alias.com/eng/products-services/maya/sy stem_requirements.shtml
    http://www4.discreet.com/3dsmax/3dsmax.php?id=966
    http://www.softimage.com/products/xsi/v42/SysReqs/

    1. Re:And this is news? by Erik+Hensema · · Score: 2, Insightful

      I'm quite sure the rendering time doesn't differ more than a low single digit number. It's CPU bound, the OS doesn't do much.

      It's just licensing cost. When you've got a render farm of 100 machines, Linux is way cheeper than Windows.

      --

      This is your sig. There are thousands more, but this one is yours.

    2. Re:And this is news? by NanoGator · · Score: 2, Interesting

      "Taking a look at the System Requirments for the more well known 3D Animation apps we see Alias's Maya and Softimage's XSI run natively under Linux. Which when you are dealing with animations that can take literally days to render for production it's no wonder they'd want to use a Linux machine instead of a Windows machine, I'm sure it cuts the time by at least 30% (totally grabbed that number out of my ass)"

      You're right, you really did grab that number out of your ass.

      There's some truth to it, though: Supposedly 3D rendering (on some apps...) renders a bit faster (nowhere near 30%) on Linux. Linux uptime is a lot better than Windows. Windows XP/2K can easily last the days or even weeks of a render. I know this from personal experience. I can tell you quite honestly I have never ever ever lost a render due to Windows instability. (Well ... after I switched to NT. Couldn't say that for 95 or 98...)

      Would Linux be preferred? Possibly, but not for the reason you've given. The odds aren't very good that you'd get much more than a few percent over Windows in terms of time getting the job done. At that point, you have to start looking at other factors.

      1.) Is Linux well supported with your 3D app? I can tell you that Lightwave's network renderer works on Linux, but I have no reason to trust it. Even if it works flawlessly, you can't open up Lightwave and see what's going on in the scene. I've also read (though I don't know from personal experience...) that XSI isn't all that stable on Linux. Can't tell you for sure that it's true, but it's certainly possible. Linux doesn't automatically make every app out there stable, it still has to be well written.

      2.) Can you maintain the systems your render farm will be on? Fortunately, Linux has gotten a good deal more user friendly over the last couple of years. However, even though I'm somewhat familiar with Linux, I'm FAR more comfortable with Windows. If I did use a Linux render farm, there would be time lost transitioning to it. The point here isn't that Windows is better than Linux, rather that maintenance is a cost of running the network, so you have to think about the staff you have available to run it. (Personally, I'd MUCH rather have Linux over Windows if I had the time to get up to speed with it. I absolutely cannot stand the 'Windows rot' that makes you have to reinstall the OS every few months.)

      3.) Will your users be able to make good use of your 3D App + Linux? This is a tricky one because in a perfect world, the render farm wouldn't care at all what the user is doing at his workstation. However, in practice, I've discovered that there can be subtle problems. For example: Linux has a different file naming convention than Windows. (Stupid drive letter.) It's possible to write a plugin that works fine in Windows but not on Linux. Depending on the app, the artists may have to take extra steps to make sure their data is properly portable for when its sent to the render farm. (This is one of the reasons I wouldn't trust Lightwave's Linux network renderer. LW is so Windows centric it's just plain a scary thought...)

      In the case of Lightwave, I can pretty much guarantee that you would actually save time using Windows as a renderfarm OS compared to Linux.

      "I think the only big name 3d animation company that is Windows only is Discreet with their 3ds Max software, which I think is really only used for games, can't think of a movie that it was used for."

      It's rare these days to find a "This OS only" shop. If you mean 'Windows dominated', then you'd find that most TV FX studios use Windows quite extensively. (Note: At least on the workstations, it gets fuzzier when you talk about just the render farm. The render farm has a lot less diversity to deal with than the workstations.) Zoic (Battlestar Galactica) and EdenFX (Enterprise) immediately leap to mind. They're mainly Lightwave and mainly Windows, to boot. Why's TV special? Short deadl

      --
      "Derp de derp."
  24. Re:So what are the reasons? Cost? Customization? by Anonymous Coward · · Score: 2, Insightful

    Not just that, but you can really fix it when it breaks.

    Currently, if a movie house is using a closed-source toolset, and there is a feature missing or a non-trivial bug causing issues with their workflow, they have to spend a *ton* of money to get the Vendor to 'fix' it for them. With an open-source solution, they can hire someone and fix it/extend it themselves for a whole lot less money.

    Production is *everything* to these kinds of businesses. *Anything* that minimizes disruptions to the production is going to be seriously considered...

  25. Re:Pixar by badmammajamma · · Score: 2, Interesting

    I think your number for a million dollars a second for rendering is WAY WAY overinflated. Lets put it this way, if Finding Nemo were done at the standard rate as you define it, it would cost 6 BILLION DOLLARS (100 minute film) to produce. So, you're saying their rendering efficiency is not only much better than normal but it's several orders of magnitude better? Or is it just the water scenes that are expensive?

    --
    Any man who afflicts the human race with ideas must be prepared to see them misunderstood. -- H. L. Mencken
  26. And this is why Nvidia's Linux drivers are so good by delire · · Score: 4, Interesting


    I read somewhere that there are a ridiculous number of Nvidia developers working on Linux driver support - hundreds comes to mind - and it is largely due to the fact that Nvidia nailed contracts with the feature film industry.

    The proprietary Linux ATI drivers (if you want pixel and vertex shader support, this is a must) now perform incredibly well, though are still an annoyance to install for many. Given that ATI seem to be the card of choice for mobile machines, I look forward to the day ATI competes in the feature film market.

  27. Re:So what are the reasons? Cost? Customization? by flooey · · Score: 3, Insightful

    From what I've heard, Linux and other open-source software is also preferred because of its ability to respond to deadlines. If you're two months from release and an obscure bug in your OS interferes with your rendering, you can't rely on the OS provider to get you a fix in a timely manner, especially if it's a bug nobody else encounters. If it's an open-source system, though, you can fix it yourself.

  28. Not Forgetting Linux gave us Gollum by delire · · Score: 2, Interesting


    Weta studios had an absurd number of IBM IntelliStations (Maya, Renderman, Alfred).

    Seems a venerable KDE was their desktop of choice. More here.

  29. Let's Calm Down a Bit by quantax · · Score: 2, Informative

    As some other posters indicated, this is not about linux being faster but more so since when it comes to cluster systems, linux has a couple advantages: low/no cost for licensing, open development environment thus easy & low-cost to work with to create further tools, stability, and customizability.

    These are the main factors, but this does not apply to anything but the rendering clusters. The actual artist-driven work is still for the most part performed on Windows systems due to the cost of hardware, availability of highend video cards & drivers, and a wider install base. Maya running on Win32 is the largest segment of the 3D users, and this is not set to change unless Apple starts getting serious and gets highend video card makers to support OSX. For small scenes, the cards that come with G5 workstations are not bad, but once you start doing more complex scenes, it becomes a slideshow.

    In the end, this is not really news as this conversion has been going on for the last several years, especially since Maya was ported to linux. But, regardless, it's good news all around as it means a user does not need access to an expensive SGI system to get familiar with cluster rendering systems and lowers the overall entrance barriers to people learning.

    --
    "What can a thoughtful man hope for mankind on Earth, given the experience of the past million years? Nothing." -Bokonon
  30. Re:So what are the reasons? Cost? Customization? by DF5JT · · Score: 2, Insightful

    "The choice wasn't Windows vs Linux, it was Linux vs IRIX. This is why SGI's stock is in the toilet."

    Incorrect.

    The choice was between IRIX--> Linux and IRIX --> Windows with hundreds of MS key account managers in LA throwing lavish parties and handing out gifts for those in the decision making process.

    Considering that, the choice made should not be underestimated in its impact, since it was a *technical* decision, not a "business" decision. Of course, a sound technical decision process will always lead to a sound business development.

  31. ILM used Origin 2000 by green+pizza · · Score: 4, Informative

    From about 1997 to 2002 Industrial Light and Magic had been using huge farms of SGI Origin2000 servers. Price to performance ratio would have been better with PCs, but the benefit of the SGI kit was the number of CPUs per single machine. Some of their render servers had 64 or 128 CPUs (the max # of CPUs for an Origin2K without having to use the special XXL kernel). This helped minimize maintainence.

    Today things like LinuxBIOS and other clustering advancements have made clusters even more reliable and even easier to admin than big iron SGI/Sun/IBM/HP.

  32. Re:So what are the reasons? Cost? Customization? by Orgazmus · · Score: 2, Insightful

    And now you are touching the key feature of open source software in a big buisness enviroment.
    To a small company the windows licenses are cheaper than implementing and testing custom features, but to a company like Pixar og Dreamworks, the cost of a couple of hundred manhours are nothing compared to the cost of waiting for Microsoft to use that money.

    --
    The system had the verbosity of HTML combined with all the readability of compiled assembly viewed as bitmap images
  33. Is it just irrational hatred of Microsoft by suitepotato · · Score: 2, Insightful

    that drives this neverending fascination with fluff non-news about where Linux is being used or is it to cover up and draw attention away from poor Windows skills, or both?

    I think both.

    I may use Linux but that doesn't mean I care to hear about every single place, thing, entity, etc. that uses some iteration of Linux. Nor do I need to hear endless fawning over Steve Jobs and Apple and OSX as if it was going to bring spiritual salvation.

    Fer crissakes people, it's just an operating system. It's not giving you longer life, making you smarter, conferring beauty and handsomeness on you, or sleeping with you (although I'm sure there's some geeks looking to cyberneticize a real doll with Linux and report on it here). I really think we need to get a grip here at Slashdot when it comes to Linux.

    I bet if my mother started using Linux at work and my company stopped using BSD it would get rave reviews and seven hundred replies in a day and a half. Meanwhile, there's actual apps being written that do amazing things running ON various OSes and we're too busy short-stroking to see the forest for the trees.

    --
    If my grammar and spelling are off, I am [distracted/tired/careless] (take your pick)
  34. OSS-friendliness? by RAMMS+EIN · · Score: 2, Interesting

    I wonder...with historically not very OSS-friendly organizations like Disney switching to Linux...if we can expect to see a more OSS friendly face from them in the near future?

    --
    Please correct me if I got my facts wrong.
  35. Re:Pixar has never used Mac hardware... by raytracer · · Score: 2, Informative

    There is virtually nothing actually correct about the parent. Pixar of course does use Mac hardware. We don't use Mac computers for our renderfarm machines, but there are vast numbers of Macs, 0and Mac laptops around the building.

    Our renderfarms haven't always been Linux on Intel either. For many years our farms were Suns.

  36. Re:Why? by delire · · Score: 3, Interesting



    Having done alot of work on high end Linux (Maya, Blender), Windows (3DSMax, Blender) and OSX (Maya, Blender) workstations, it's safe to say one can't look past Nvidia on Linux for raw polygonal churning power. Linux is an industry standard 3D animation platform, renderfarms aside.

    Perhaps with a substantial license deal Apple may deliver a distribution of OSX to fit, but out of the box it's a poor performer. Of note is that the proprietary Aqua interface hits the GPU for fast 2D blitting. The last thing you want is a DE that hogs your precious GPU for mere interface beautification. Similarly relative customiseability is important where mission critical work is to be done, for this reason OSX is significantly less viable. As for Windows, it's barely safe for home users let alone dear Gollum.

  37. Why Linux is a better cluster platform than Win by typical · · Score: 4, Informative

    Care to elaborate?

    Because it's a pain in the ass to run headless Windows boxes compared to headless Linux boxes.

    Because Microsoft's idea of clustering is a couple of failover webservers, not a large, highly-parallel computer? (Granted, this makes sense for Microsoft -- "clusters" was a sexy word a couple years ago, before "grid computing" got to be sexy in business rags, and their customers generally have no need for massive parallel computation, but do run web servers and do read magazines that tell them that they need clustering technology deployed yesterday).

    Because a minimalistic Windows setup is fatter and eats more disk space and memory than a minimalistic Linux setup, and buying more resources for a couple hundred nodes so that you can run some background crap produced in Redmond is pretty plainly a bad idea.

    Because clusters are done by the sorts of smart people that do automation and systems development, and a large chunk of those sort of people can personally benefit greatly from Linux, so they're more familiar with Linux than Windows.

    Because there's no reason to bump up your cluster's cost by a significant amount for software licenses when it doesn't help you at all.

    Because Linux generally outperforms Windows (especially when you're looking at kernel-level performance), and the sorts of people that get large, expensive systems like this have a lot of interest in getting their code running as fast as possible -- doubling the compute speed means that they require half or less nodes in their cluster. If your kernel can shove more data onto the network more cheaply or context switch a few more times, you're more valuable.

    Because they can customize a Linux system much more easily to do whatever they want than the Windows system. I was pretty appalled when someone managed to mess around with an new ATM up at Carnegie Mellon University and left it on the Windows desktop...and the thing was a full-blown Windows box, with all the software installed and whatnot, NOTEPAD, you name it. Not only is that just not professional, it's a sign of the developers having to fight the system to achive the result they want. Linux won't fight you if you want to customize it.

    Linux is open source. If you're working on the kinds of projects where a lot of serious large-scale parallel computing is involved, you may well have significant systems expertise available, and hacking your Ethernet drivers or the kernel to speed things up may be reasonable. A large chunk, perhaps a majority of Linux Ethernet drivers started life with Donald Becker, who was working on Linux clustering for NASA, if I remember correctly. The man needed some high-performance networking code, and had the ability to produce it.

    And finally, last but not least...Windows isn't fun. Linux is fun. Okay, you can't really put that on a checklist somewhere, but if someone likes what they're doing, they're going to do a better job of it. I'm working on a cross-platform project for my employer at the moment. The Windows developers are kind of apathetic, spend a lot of time chatting and whatnot, but the Linux port guy is a machine. He's *into* what he's doing, he's excited about it. Of course, that's anecdotal evidence, but I've seen a lot more enthusiastic people hacking Linux software than hacking Win32 software. [shrug] Make of it what you will.

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    Any program relying on (nontrivial) preemptive multithreading will be buggy.