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."

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.

Virtual appliances

[fatnicky]

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.

*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.

Re:*Another* Layer?

[Cheeze]

Virtualization is probably best used in test environments. Copy a normalized disk image and run from the copy to see how the software interacts with the hardware or operating system. When you're done testing, no need to mess with any hardware, just delete the disk image.

It should also be good for those environments that do not require much performance. if you are running a specialized java app and you consolidate 2 hardware solutions into a virtualized solution, you might need to have 2 different java compilers installed. You wouldn't want to join these two java applications onto the same logical hardware, but you can put them on the same physical hardware.

Microkernels++: Just in case you dont remember

[LordMyren]

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