Modern machines have far more power than what you need, which can lead to CPU problems. What do you do? David Chisnall suggests virtualization and paravirtualization applications such as Xen, which is discussed in this article.
The Need for Virtualization and Xen
About The Author
Ex-programmer, ex-editor in chief at OSNews.com, now a visual artist/filmmaker.
Follow me on Twitter @EugeniaLoli
2006-04-03 7:34 amskx2
Nice to see people pimping my articles rather than having to do it myself
I’m a big fan of Xen and use it a lot for Linux-on-Linux, but I don’t really need to run Windows very often. For a lot of companies it would be a big win to run Xen for free – but with the opening of VMWare player it might not be so important.
I’d expect the biggest Xen users will be hosting companies, and the like, so the lack of Windows in that scenario isn’t a big deal.
How are you going to get Windows to run in Xen? Last I heard the Xen crew was able to get it to run but they would not release the instructions on how to do it.
2006-04-03 3:53 pmsegedunum
How are you going to get Windows to run in Xen?
Windows can already run on Xen, bizarrely, but it cannot be released or used because of licensing restrictions. This is because unlike with VMware, the OS does need to be ported to work with Xen. To get around this problem, support needs to be provided by the hardware in order to run Windows. AMD’s version is Pacifica, Intel’s is called VT.
That’s the difference between Xen and VMware. VMware allows you to run full operating systems, completely unmodified, on the VM software environment and the OS will totally believe that it is running on hardware. No porting, nothing special to be done. Thus, VMware can run Windows. To say this is difficult is an understatement, because the x86 platform is extremely ill-suited to being replicated like this and VMware have had to replicate every nuance and quirk to get x86 operating systems to work properly unmodified. The sacrifice for this convenience is of course performance.
The problem with Xen right now is that it just doesn’t have the management tools that VMware has. VMware have tried to quell Xen somewhat by giving what was GSX Server away for free, but to be honest, I wish they’d just have cut the price of GSX and kept it fully supported. That’s why, if you’ve been to a VMware roadshow, you get the VMware people giving you this bizarre message that VMware Server is not for production systems and you should buy ESX. Everyone who’s using GSX Server, and the Server beta, knows that this isn’t true and it serves a reasonable amount of people well. I think they made a mistake there.
I believe what SEJeff meant by ‘dual core AMD processors built-in virtualization’ is the one with pacifica, which would allow unmodified operating systems to be installed and run on Xen including Windows. If you have kept reading tech news you would already know it by now though…
2006-04-03 4:35 amSEJeff
You sir are correct. I don’t guess he pays attention to tech news yet he reads osnews? Kind of weird huh?
Period. End of story. Without support for Windows, VMWare will continue to dominate this market, especially after they’ve made the basic product free-as-in-beer. I’m in the process of building a multipurpose host for a small office; I need to be able to run several different OSes. I’d much prefer to run Xen (I run it at home, and am going to use it on my colocated machine), but I can’t because the accounting software the company runs requires win2k or 2k3.
I don’t have time to wait for the AMD product to come out.
BTW, that article reaches a new low in the new trend of short multipart text, lots of ads.
2006-04-03 6:48 amchekr
“Period. End of story. Without support for Windows, VMWare will continue to dominate this market”
I really dont think you understand what xen is and what it aims to achieve.
Besides this I can see that this may be an issue in your usage case. Not everyone has the same usage requirements that you do however, before making “Period. End of story” like statements perhaps you should consider this.
Xen serves my need for creating testing environments. I guess Xen has more ambitious aims, but I don’t care much.
Xen just blast me. On my laptop it’s cool, though it is useless, but fun to do. Actually when you consider this, it is also cool to have UML. And well vmware also works. Now my laptop is a Debian.
Xen team has released some measurement on their web site. I dunno how they did the test. But I know one thing for sure: with Copy-On-Write, anonymous memory, and Skas3, UML performed way faster than VMware on my laptop. Sure Xen also performed much better than both of them.
I see a lot of articles on how ‘I rocks with Xen on my Debian’… But because of my work I had to virtualize a RHEL4 whose HDD are SATA drives. After 2 weeks I gave up. I couldn’t get a virtual RHEL4 to run above a RHEL4. Neither with Xen nor UML.
Well I am glad we still have VMware. However I would have prefer Xen and I am happy that Redhat has told they would support virtualization with Xen for RHEL5. I am sure they’ll help a lot to make it easier to virtualize something else than a Debian.
I would like to rectify my previous comment: I find it a bit “wierd” and biased towards Debian.
I just wanted to emphasise that Xen is usually a need because of performance in company like mine.
Second there is also a nice alternative as UML (and Vserver – though I did not talk about it cause I find it more difficult to put in place)
Third, the move made by RedHat will help support more hardware and better integration with linux/distros. So all good.
I guess he’s right in that the vast majority of pc buyers use their machines more for heat dissipation than anything else. For the rest of us, smile and on to the next article.
is pacifica and VT audio and video hardware accelerated ?
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2006-04-03 12:05 pmMark Williamson
Pacifica / VT includes no support for accelerating audio / video for guest virtual machines.
Xen *emulates* a Cirrus video card with some acceleration (I think) but it still must be emulated in software. It would be nicer if the *real* video card was aware of virtual machine displays directly – some hardware manufacturers are working on this I believe.
Audio devices are also emulated in software and then output to system sound device.
There are plans to improve performance of the graphics device in various ways, including potentially adding a “Xen-aware” display driver to the guest, in a similar approach to that taken by VMware and other vendors.
That it is sitting idle?
This was really a great, easy-to-understand and enlightening article. Before this I never understood what about Xen required the OS to be modified, and why. Thanks for the link, Eugenia!
I know Microsoft is working on supporting virtualization with their upcoming Virtual Server product, and from the other article I see that they are supporting “non-MS OSes”. I’ll be interested to see how well it works, and if they also make running Windows on Linux easier to do in the future.
It seems to me the real wildcard is Apple and Mac OS. In my view, this is one OS that could benefit perhaps more than any other from virtualization, but I’m worried that Apple might be short-sighted on this one. Although I’d guess that Apple could get Xen working without too much trouble, I’m worried that they’ll think it’s not important to the majority of consumers….
However, I for one greatly appreciate the benefits that virtualization could provide to the average consumer. Imagine playing Windows games on Mac or Linux without rebooting. Imagine playing DOS games issue-free on any new OS, for that matter! Woot!
Anyway, apparently none of this will really take off until the next generation of chips. Let’s just hope Apple gets with the picture.
Edited 2006-04-03 14:11
Is anyone of you aware of a tutorial wich describes how to write a hello_world_kernel wich can use Xen ? That’s something I’d kind of like to do as a hobby project
is ok, but I like to be spoon fed and read some code rather than (dry) manuals if I can.
2006-04-03 3:22 pmMark Williamson
You could try reading the code of the Xen “mini OS”, which implements functionality (start of day code, console) for a guest on Xen.
It’s in the source tree, but you’re probably best off using the version in -unstable because it’s had a load of updates / fixes recently.
I’m afraid you’re on your own with reading the source at this time. There’s the Interface Manual which might help explain what various features do. Some folks are looking at publishing Xen books, which might explain more stuff depending on what they decide to focus on.
Well actually Xen provides a pretty good way of isolating things like say your web server or database so that you have a fairly secure backup on a virtual machine. I was wondering though if any of you know what happened to usermode linux? It used to do similar things granted that Xen is a lot more powerful has more features and probably runs faster.
“Modern machines have far more power than what you need, which can lead to CPU problems. What do you do?”
Ahh yes. My server is consistently NOT overloaded. I really must do something about that. I’ll leave the silly virtualization crap to the mass vhosters that don’t know any better.
I’m waiting for the dual core AMD processors with built-in virtualization to come down in price so normal mortals can buy them. Then, I can run windows on Xen at native speed and still stay in Linux.
Xensource needs to clean up their act and start trying to merge with mainline. Xen is awesome from my experiences with it and Debian: