In some ways it's the equivalent of tabbed browsing or application windowing - virtualization of the OS creates efficiency by dealing with multiple divergent contexts at the same time.
And then they moved onto a different project, and their browser bookmark wasn't there.
And now they're not happy, because Windows lost their stuff.
(Because very little of what most people do can be compartmentalized that much - and Windows is great because it allows you to multitask, which you can't do if everything is in a different VM.)
Most people don't keep their filing system very organized and when it comes to bookmarks even less so. Context is often a more efficient way of recalling what you did than a directory name - particularly over longer periods of time such as several months.
And of course, you can multitask across virtual machines - I often have two or three open at once because I need access to software which runs on a legacy version of Windows and I run Facebook in it's own exclusive VM.
At the same time I will be working on a project on the host OS. And there is no need for interconnection between any of them.
And VM's solve a lot of legacy issues, cross platform compatibility issues (e.g. windows phone apps) and Microsoft has already developed methods of integrating VM's with the host (see Windows Virtual PC and XP mode integration).
If we're talking about having them all having access to each other, then I can't see what you gain by putting apps in different VMs.
And in my writing side projects, I may leave a project for several months. So that's where I realized the value of VM's - the one's I use have survived an upgrade from XP to 7 with the same open windows and without any software reinstallation (and of course without any recreation of bookmarks). I'll add that they are also descendents of previous virtual machines used for the same purpose but different projects. It is more efficient from a workflow perspective to have six copies of Open Office each pointing to the relevant context than to reconfigure one copy each time the context switches.
To put it another way, the way in which one develops software projects from a custom starting point and the way in which references persist across IDE sessions during a project due to saved state are not unique to software development. They are indicators of the features which facilitate efficient project execution timelines.
The current demand for virtualization is, to a significant degree, an attempt by admins to get control of their own hardware back from Microsoft. Putting MS back in charge of the lowest layer hypervisor seems like it could sort of defeat the purpose. Or maybe they'll play nice this time?
What do you mean?
Interestingly, I view the current state of the world as too much sharing -- VMs are just super process isolation =D
It turns out that one of the apps people really need to run multiple instances of is Windows itself. This is largely Microsoft's fault for bundling every app including the kitchen sink in the OS platform itself. As a condition of using their clean little high-performance kernel, you had to accept a web browser and home-user-friendly userspace.
Little surprise that people are kicking the whole package off of Ring-0 and substituting something like vmware for their $five-figure server hardware.
It's that super-isolation that actually allows multiple apps/roles/data categories to finally share the same hardware.
This tradition started ~98, with Microsoft. Before that, when servers were Suns, IBM and Digital, every server had lots of roles.
Somehow, microsoft convinced the world that it's better to have one server per role (and pay them for some more licenses).
We should be virtualizing the software, not the machines. Oh wait, we already are: JVM, CLR, Python RT, good-old-fashioned processes etc...
Virtualization is just snake oil. I don't see a real use for it TBH and I work at a place that drinks the VMware kool aid. All it does is cost money, use up resources and excuse incompetant administrators from having to plan properly up front.
Virtualization should not be at the hardware level - that's just retarded and another unnecessary product.
However there are three facts that get in the way of doing the right thing:
(1) Does it run Windows?
(2) We've got Intel and AMD making PC virtualization acceptably fast nowadays, so it makes sense to just use that.
(3) Isolation between processes is not very strong [not sure about virtualenv] but between machines is a great deal stronger because people have a lot more experience protecting networked machines from each other.
... and backed by hardware!
2. It's acceptable until you whack several kernels and OS' on a machine, all running lots of processes at which point everything suffers. Cache locality goes AWOL, cache utilisation is shared, bus traffic goes up, so does latency and performance suddenly plummets.
3. It depends on the environment. Virtualenv just provides a consistent python software environment which can be isolated from everything else on the machine. As for other things: Look at FreeBSD's jails - that's as far as it should go. Linux has ulimit and decent security. Windows has NT which is actually damn good and provides very good process isolation with respect to memory, CPU and IO no less.
If we needed virtualization, we wouldn't have processes.
Anyway, you can't compare "virtualenv" which seems to be some sort of Python interpreter hack, with full virtualization. They are completely different things, with completely different use cases.