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Experiences with Replacing Desktops w/ VMs?
E1ven asks: "After years of dealing with broken machines, HAL incompatibility, and other Windows frustrations, I'd like to investigate moving to an entirely VM-based solution. Essentially, when an employee comes in in the morning, have them log-in, and automatically download their VM from the server. This gives the benefits of network computing, in that they can sit anywhere, if their machine breaks, we can instantly replace it, etc, and the hope is that the VM will run at near-native speeds. We have gigabit to all of the desktops, so I'm not too worried about network bandwidth, if we keep the images small. Has anyone ever tried this on a large scale? How did it work out for you? What complications did you run of that I probably haven't thought of?"
Get some Sun Microsystems SunRays. Seriously.. thats exactly how they work. Your session can be saved on server and resumed anywhere else you plug in your smart card. One server and all of the terminals you need.
LTSP.ORG does somthing similar. You run X clients on a common "server" and view it with an X server on almost anything with 64 megs or more of memory.
For Windows, use roaming profiles and default installations. For Linux, rsync works quite well for the base OS (say, a staggered start time at night based on IP), with OpenLDAP doing auth and home dirs stored on central server(s) and mounted via NFS. New system setup becomes a knoppix CD, partition the new drive, format partitions, mount them, rsync the distribution to the new machine, chroot, and setup boot loader. You could of course script all of this, and this is very similar to what I do for kiosk systems (Linux/Firefox setup), except the kiosks don't change, so it's just a big tarball via sftp instead of rsync. You could also do tarballs, and keep the last few versions as backups in case you screw something up. If the hardware is identical, use the distribution of your choice, but if there are several different systems, you may want to use one with good hardware detection (like knoppix).
--That's the point of being root, you can do anything you want, even if it's stupid.
I think I have to disagree. Most of the better gigabit nics out there support PXE boot. Get a small boot loader image going. If these will all be on the same lan segment, at boot time it will grab the latest loader image, boot the small loader (~2MB). The loader can then boot the full OS image.
You can then just capture or encapsulate the computing session to an image file. It's not a full virtualized environment, as you still get the benefits of the cpu horsepower at the workstation, but if corruption occurs ou just roll back the session file. I think.
This is how Windows hibernation functions in a nutshell, just dumps RAM to a file I think. I haven't tried this in practice, but it should work.
Karma: Chameleon (mostly due to the fact that you come and go).
You don't need to "carefully" do anything. Folder Redirection in Windows was created just for the task. It's a feature that was introduced with Windows 2000. Beyond that you can use SMS and custom office installs to have everything configured properly everytime someone logs in. Mandatory profiles ensure that everything stays clean and spyware free. Which weaknesses are you referring to?
Beyond that I'll go and say that this approach is bomb proof and by redirecting files on to the servers which requires surprisingly little overhead you ensure that when users float from machine to machine they have all their application preferences and data. Settings can very from machine to machine with different version of software and whatnot but again, SMS will fix that.
I think we can all agree this is not a good use of virtualization. It would be very resource intensive and a simpler PXE solution already exists. With PXE you don't even have to have all the same hardware, just the proper drivers. SMS will take it from there installing the rest of the third party apps whatever they may be. Can be done from start to finish in under 30 minutes which is about how long it takes to fully restore an image. Of course over a gigabit link the time might be reduced but Windows will take a good 10 - 15 minutes to install over the network so it wouldn't be unreasonable for everything else to take another 15 minutes depending on how much there is. I know in my basic setup with Windows and Office its about 20 minutes give or take depending on processing speed and quality of hardware.
This is a different kind of a VM. .NET and Java run application logic with their own type of VM that allows their applications to interact with the OS, in many cases, just like any other native application. VMware and other VM solutions attempt to emulate an entire host computer to run an operating system, which can then run applications. These applications are constrained to accessing only the things available to them in their operating system and cannot interact with the host operating system, except through emulated networks and devices.
.NET simply make the native operating system's 3D APIs available to its applications. A full VM solution would have to implement a "virtual" 3D-capable video card that a guest OS would be able to use, and then find a way to hook that emulated video card up to a variety of real video cards. This is considerably more difficult.
Java and
VMware has actually had 3D support for a while, but it's been painfully slow. The latest versions do make some attempt at using hardware 3D acceleration through the host operating system. I'm not sure how well at works, though.