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An Overview of Virtualization
IndioMan writes to point us to an overview of virtualization — its history, an analysis of the techniques used over the years, and a survey of Linux virtualization projects. From the article: "Virtualization is the new big thing, if 'new' can include something over four decades old. It has been used historically in a number of contexts, but a primary focus now is in the virtualization of servers and operating systems. Much like Linux, virtualization provides many options for performance, portability, and flexibility."
IndioMan writes to point us to an overview of virtualization -- its history, an analysis of the techniques used over the years, and a survey of Linux virtualization projects.
That article had the virtue of being a virtual cornucopia of information.
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Virtually anyone can do it!
Just wanted to point out that qemu can also do virtualisation on Linux, just like Vmware, with a closed-source kernel module. It works quite well too. http://fabrice.bellard.free.fr/qemu/qemu-accel.htm l
This article is an okay overview of many of ways virtualization is now being used. As an aside, has anyone else noticed Apple seems to be missing the boat this time? They're certainly benefitting from virtualization with several players in the market providing emulation solutions and tools now that they are on Intel, but Apple themselves seem to have done nothing and not even provided a strategy. Servers are moving to more virtual servers on one real machine, but OS X's license forbids it from fulfilling that role. Tools for using OS X as a thin client for accessing remote virtual machines are likewise weak. Apple hasn't even provided a virtual machine for their customers to emulate old macs so that users can run OS 9 apps on the new intel machines and they restrict redistribution of their ROM files to make 3rd parties unable to do this. No mention of adding VM technology to OS X has been heard, despite its inclusion in the Linux kernel among others.
Does Apple have something against VM technology? Are they simply behind the times and failing to see the potential?
"Virtualization is the new big thing, if 'new' can include something over four decades old."
You just wait. Next thing you know we'll be running Lisp machines under our virtualization software. And then there's going to be a new remake of ADVENT and the Great Worm. And a new AI summer.
Please correct me if I got my facts wrong.
I work at a small ISV which just bought SourceForge, Enterprise Edition which is an Apache/JBOSS/PostgreSql/CentOS app for managing SDLC. For a company of our size, they package this as a VMWare image. Installation is incredibly easy. I can definitely see how free virtualization can be a big boon to companies selling and/or consuming web applications for small deployments.
The article seems a bit light on qemu too.
An idea that I've been toying with lately is what if we got operating systems targeting virtual machines, especially ones that expose a simplified interface rather than trying to emulate a real machine. Instead of having to duplicate drivers for every piece of hardware in every OS, drivers would only need to be developed for the virtualization environment, and operating systems would only have to support the interface exposed by the VM.
Please correct me if I got my facts wrong.
MOL is a true work of genius. Even on pretty old PPC hardware it functions with almost no slowdown. (Linux host, OS X and Linux clients). Compared to contemporaries it had no equal - the current generation of products on x86 are just starting to catch up. I'm most impressed with the way my powerbook can sleep (close the lid) under Linux and all of the hosted sessions quietly pause themselves with no problems. They even resume a network connection perfectly on waking up.
It'm glad to see similar happening on x86, finally, as it's one of the things that really made PPC based machines special. (There is some documentation for MOL and Kubuntu here.)
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Virtual appliances will drastically change the way tech sales is handled in 2007. Instead of a sales rep promising their product can perform, they'll now be immediately asked to put their VM where their mouth is.
I for one look forward to vendors coming in and pitching me their software. The ones that can instantly show me the product in a virtualized session running on their laptop will be the ones that we write the check out to.
I for one look VERY MUCH forward to placing our systems on virtualized resources. It'll make us look like a million bucks while saving a million bucks.
This is also great for small businesses who need a quick deployment. I love being able to instantly expand my hardware to accommodate new setups.
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For the home user virtualization can be used as a separate PC to surf the net without fear of malware, when you are done surfing just restore the VM to the "clean" state, think "your pr0n browsing PC". You can also use it to test software before contaminating your host PC with stuff you decide not to keep. I visualize it as a sandbox to play in before messing up with the "real" system.
Check the vmware player appliances, there are lots of good ideas there, many of them are for business use but there are several that can be used at home.
For the developer / tester virtualization provides a set of target operating systems to test / debug the software on without need of having the actual physical hardware.
Of course, in the data center it is the next big thing, too many advantages to list here.
moi
But in theory, it bothers me. The basic idea (as I see it) is to provide an isolated environment for applications to run. But that's what the OS was/is supposed to do in the first place, and typesafe languages (like Java) also do much of the same thing once again! (E.g. I see no inherent reason for virtual to physical address translation when running Java applications). The biggest commercial application I see for virtualization is server consolidation. Why not just run all those server processes within the same OS? Yes there are good reasons, but is virtualization really the most efficient solution to those problems?
Maybe virtualization is the best compromise given the legacy that computing currently has, but I wonder if some clever researchers have expressed a vision of how all the same ends could be accomplished much more simply and consistently. Or do all these layers upon layers of abstraction really provide necessary degrees of freedom?
and had serious issues with stability and networking. I detailed my experience at my blog if anyone is interested. I also tried using the Linux version of Parallels and had similar issues. If anyone has gotten Vista to run under Xen I would be very interested in your feedback
This may be a little off-topic, but I noticed that the article claims that Xen runs on FreeBSD. I was under the impression that Xen support on FreeBSD was still a work in progress, which the Wikipedia article seems to confirm. Can anybody comment on this?
Uhm... I started using it on the PC platform in 1998/99 with VMWare on RedHat 7. I was amazed when I saw I could boot a Windows 98 system simultaneously with my already running Linux system on a lowly Pentium MMX 233 with 32 megs of RAM. Then I found out that what I thought was new back then was something the big iron world had enjoyed for decades and originated in the 60s. It was just new to x86 is all come 1998/99. Since then, I've moved onto Xen for Linux which is rather amazing in terms of performance and flexibility if you paravirtualize the system. I've got three VMs running on an old Pentium II era Celeron at 400 MHz with 384 megs of RAM. That system has enough horsepower to do the following for my network:
Internal: DHCP, DNS, postfix SMTP server for internal clients, Squid proxy, OpenVPN MySQL DB, DBMail IMAP services that use MySQL as the backend. All in 128 megs of RAM. And they all perform smoothly and quickly.
External: DNS, postfix SMTP server for spam filtering and relaying to the virtual internal SMTP server, OpenVPN server. All in 64 megs of RAM.
I plan to add an Asterisk PBX to that same box for a third VPN so I can have private VoIP with my OpenVPN users (all friends and family as I'm talking about a system at home, not at work).
I've, of course also played with Virtual PC, Virtual Server, QEMU and poked at OpenVZ. For me, a decent virtualization solution has to be able to run other OSes to count as good which is why certain virtualization solutions don't do much for me. If I need access to Windows, I want to be able to do it without wasting good hardware on it. That's why UserMode and Linux Virtual Servers (more akin to chroot jails) do absolutely nothin for me other than when I'm building a Gentoo box. But, this is not the big new thing. It's only that MS is making waves with it now... typical.
-"...bad old ideas look confusingly fresh when they are packaged as technology" - Jaron Lanier (Digital Maoism on Edge.o
You'll probably never see this comment, but so be it...
Where we've found it incredibly useful is in 3 cases:
1) Any server where end users may cause damage. In our case, we have a remote desktop available to the end users via Citrix. Yes, it's secured -- but there's always SOME chance that an end user will mess it up somehow. By running the Citrix server in a virtualized non-persistant environment, any damage can be corrected by simply rebooting the virtual Citrix box.
2) Very low utilization applications that are required to be on their own server for support purposes. There's tons of Windows financial & business apps that won't play nice together, or are simply unsupported by the vendors if there's anything else on the box. The easy solution is to simply load these lightly used images on a single host box.
3) Migrating services. If an app is installed in a virtual environment, and the user population suddenly triples, all you have to do is migrate the virtual image to heavier duty host hardware.
The original plan for microkernels was to create more componentized runtime environments, so you could dynamically create virtualized OS's as a collection of the active componenets you needed. Very much like chroot, but pervading way beyond file systems and in to running libraries kernel modules and devices. The tooling was never here, but many people had stary eyes for esssentially a mix-and-match environment that would let you configure and cobble together operating environments at will, and maintain strong privledge seperation.
It really is a pity we gave the whole project up and decided to just implement YET ANOTHER page table in hardware, rather than try to solve the PIC code layout, IPC performance issues, and wrestle with building a new dynamical component based environment. I think we'd see virtualization on a much more pervasive level and a much stronger conception of mobile code, stretching all the way to embedded devices. As it is, the hardware virtualized environments are so insular from each other that there is a) no reason to run it on embedded systems (since integration is all application level, tracing through pretty meaty stacks) (watchdog systems aside) and b) it would impose colossal power consumption needs for mobile devices since it has to run each OS seperately.
Virtualization as we know it is a terrible terrible excuse for unix never having built itself a sufficiently dynamical and configurable environment. Two thumbs down. As cool as running multiple OS's is, it should not have been necessary in the first place.
LordMyren
Amdahl was the first to offer physical machine partitioning in the mid to late eighties. IBM finally came out with PR/SM (Processor Resource/Systems Manager) some years later. MDF provided complete isolation of resources between two or more partitions. There were no shared channels, intercommunication was done with a Channel-To-Channel connector. This provided a secure, isolated development/test/QA systems at a reasonable price. It was all managed at the macrocode level, which had a Unix-like shell.
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> The kick ass server being a Celeron 2ghz machine with 256 megs of ram.
There is a note of cynicism in your statement, but yes you will need adequate hardware and resources to take advantage of virtualisation. You should not expect to run two identical instances of a server environment on your hypervisor and expect a performance increase (depending on utilization of course). Also keep in mind your host os is going to need resources to run the show. This is where a stripped linux install has the advantage. One problem is people run their hypervisors on windows which really wasn't intended to be a multitasking server OS in the first place. They expect to see nice fluid resource management and it just doesn't happen and they get aggravated and try to throw more hardware at it with very little improvement. Also, keep in mind that Vmware and Xen are two separate types of hypervisors. As I understand, Xen is the operating system and hypervisor all rolled into one, whereas Vmware is an additional layer on top of the host os. YMMV with either.
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Edit your
Add the following:
mks.enable3d = TRUE {- Requires acceleration on the host, because it passes things directly from the guest.
svga.vramSize = 67108864 {- This line increases the vram size, you might want to customize it.
vmmouse.present = FALSE {- This disables the 'absolute' pointing device in the guest OS (as applications that require directinput relative mode needs to turn off 'relative' mode in the guest). Note: If you unset this option, you should also turn off the preference for motion ungrabbing in the settings dialog
Unfortunately not all aspects of 3D acceleration on the guest are actually accelerated -- Which are some of the following:
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The games I've seen VMware running myself... The sims, World of Warcraft, Half life and Second life.
Change is certain; progress is not obligatory.
No, I get some apps running faster in the VM than natively. I can only make the claim for number-crunching apps (EM solvers and the like) running in a 32-bit XP VM on a 64-bit linux host (running VMWare Workstation 5.5x), no swapping going on. But yes, definitely faster in the VM than on the same hardware running XP natively. Maybe it's that the VM presents fewer overheads to the XP OS, with it's simplified virtual hardware. You would expect at least nearly comparable performance for number crunching only (almost no disk, no graphics). Graphics intensive apps run like shit in the VM.
-pete
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