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."

Comments

Re:Apple

[diamondsw]

Let's see, why don't they do virtualization...

• They don't want you to use OS X in a VM, as it makes it trivial to use it on generic PC's, which eliminates the vast majority of their revenue.
  
• They don't include virtualization software themselves as Parallels and VMWare are doing a good job if you need such a thing, and they don't want to alienate them.
  
• And not strictly virtualization, but you mentioned it - they don't want to make it easy to use OS 9. It's been dead to them for years (and porting Classic to Intel would not have been easy, given the way Rosetta works). Meanwhile, they do nothing to hinder or help SheepShaver and others; the ROM files needed are available from Apple's website (although not easy to find).

None of this is hard to figure out. Yes, there are reasons it would be nice, but it's pretty obvious why they're not too keen on it.

*Another* Layer?

[timeOday]

In practice, I really like virtualization because it allows me to boot up Linux and run MS Exchange and Office, and most other (non 3d) Windows software using VMWare.

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?

Re:Apple

[99BottlesOfBeerInMyF]

They don't want you to use OS X in a VM, as it makes it trivial to use it on generic PC's, which eliminates the vast majority of their revenue.

I'm sure that is true, but do they have a plan for what happens when/if the industry moves toward virtual machines on the server? Are they just going to let OS X server die, or try to target only really small businesses? What about thin client support? if more and more VMs start running on big hardware and exporting to thin clients do they have a plan to provide better support for those clients? Integrate with those UIs? Are they just assuming none of this will happen?

They don't include virtualization software themselves as Parallels and VMWare are doing a good job if you need such a thing, and they don't want to alienate them.

It is perfectly understandable not to include a VM in their workstation, but that does not preclude kernel level support for virtualization, including API's and hooks for interoperability. What about hooks for supporting virtual machines like Parallels, but treating the apps as more "native" with Windows or Linux binaries showing up as icons in OS X?

And not strictly virtualization, but you mentioned it - they don't want to make it easy to use OS 9.

Depending upon how access to OS 9 apps is accomplished, it certainly is virtualization. I certainly understand not including it in a the default install to discourage the use of OS 9 apps, but making it hard to find and install your own VM of this sort is counterproductive, in my opinion. Even PS3's provide a way to run PS2 games.

Meanwhile, they do nothing to hinder or help SheepShaver and others; the ROM files needed are available from Apple's website (although not easy to find).

SheepShaver is useless without ROMs, the discovery of, extraction of, and installation of is well beyond the capabilities of even many advanced users. Apple does not allow the SheepShaver project to redistribute those ROMS or include them in a pre-build binary. That certainly hinders the project a lot and prevents it from ever being user friendly enough to attract a significant body of developers. It seems like a tiny bit of privilege from Apple would go a long way here, but they withhold it.

It just seems like VM is a very promising new technology that MS and Linux distros are leaping at, and which is finally evolving a few standards. Ignoring it on so many fronts, seems dangerous to me, akin to MS ignoring the internet until the final hour. Ignoring some of the fronts on which VM is making inroads is one thing, but ignoring them all seems almost like a cultural bias. I wonder if maybe the term is taboo at Apple, since they are worried about it one one front and have applied a policy a little too liberally.