What is Virtualisation?

Clarifications

Full virtualization, in computer science, is a virtualization technique used to implement a certain kind of virtual machine environment: one that provides a complete simulation of the underlying hardware. The result is a system in which all software capable of execution on the raw hardware can be run in the virtual machine. In particular, this includes all operating systems.

It simply means that you can create an environment that is similar to useing your normal PC. It is a PC within a PC. This is created by creating a Virtual PC (Machine) which really is a file on your Hard Drive that acts like a hard Drive and you can install an Operating System to that File (Machine). You run it in a Virtual environment. I have found that Virtual PC 2007 is easier to use than VMWare. Useing Remote Access is similar as you are controlling another PC from the PC.

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Virtualization is taking a single computer (the hardware)and installing more than 1 copy of an operating. So let's say I have only 1 server and want to run a web server and an email server. I can install VMware and then running that program can put in say the Linux install disk and install Linux "Virtually" and then name the install Virtual1 for example and then install Microsoft Exchange on a different virtual server. So 1 computer can run both Linux and Windows and be a web server and a email server. The 2 virtual servers are managed by the VM ware software. Normally you could never install Linux and Exchange on a single computer. For a PC you could install XP and Vista and Apple OS on a single computer so you can run XP and Vista at the same time and switch with just a keystroke. You need alot of RAM though.

Thanks Rob and Mr Dead Head for your trouble in trying to answer my question. But I still don't understand this.

A while ago, I ran XP Pro and XP home on partitions on the same computer. Now I do not see that this was virtual: they were "there"! I could choose Pro or Home, just as I can now choose either of my computers via Remote Desktop, or as I can choose, Firefox, IE or Chrome, Word or Excel.

I cannot see how this is "virtual"!

Thanks again,

Paul

... Error Checking. If you right click drive C and choose properties, then go to the tools tab, you'll see it there.

I thought that everyone had used Windows 98. That photo is of my XP PC running Windows 98 in a Virtual PC. A lot of the old timers here would be familiar with that screen.

What you are refering to is Dual Booting using two Physical Hard Drives or Partitions.

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You said: "I cannot understand how something can be "there" but isn't!"

It really IS there. The primary OS ignores the fact that it's there because it's operating within the VM software environment, effectively being cloaked. The same happens when you're running within the VM environment. The virtual OS can't see outside of the VM environment. It doesn't know the primary OS is present.

So, you can think of the VM software as an envelope. What is outside of it can not see what is inside. What is inside can not see what is outside. Neither the outside or the inside are aware of each other. But, the VM software is aware of both.

Thank you for persisting with this - and I am
very impressed that you remembered my earlier
problems.

Right now I have the two computers working
pretty well as I wanted them to.

Remote desktop works as does "my network
places" all via a cross-over cable.
Sometimes I have to log in on the second
computer before I can connect to it remotely,
and sometimes not! I have bought a cheap VGA
switch for use when either I have to log in
(spare keyboard stays on floor) or each week
when my IP address changes itself (that is
the IP address of the second computer). Then
I run CMD and ipconfig /all to get the
necessary information and after that Remote
log in remembers it - excellent.

I have to say I am very pleased with remote
desktop, so I have to offer another big thank
you to G-Man who came up with the solution to
make it work.

I would genuinely like to understand VMWare
etc. but frankly I think it's beyond me at
present!
Thanks and best wishes

Paul

When you run a OS inside a OS virtually it removes a lot of issues that you would otherwise need to address. As the Virtual OS has no direct contact with the hardware it only sort of works with the running OS which to the Virtual OS is the hardware. The Virtual OS is Isolated from the Hardware and has no direct contact and doesn't need direct access to it's own individual HDD partition or space in RAM.

It effectively tot he Hardware and everything around it becomes nothing more than a running application within a program in this case VM Ware. The actual Partition Created isn't [b]Real[/b] it only exists within the confines of the Software that it runs on. A Real OS has direct control over the Hardware that it runs on but a Virtual OS doesn't have this control as it never actually has direct contact with the Hardware what it thinks is the hardware is nothing more than code running within a Application that fools the OS into thinking that it is actually controlling something. The role of a OS is to provide an Environment to allow some for of work to be done be that play games run a Giant Data Base or whatever the OS allows the application to run but in the case of a Virtual Environment the OS doesn't even do this all it actually controls is nothing it's only interfacing with some cleaver programing that it thinks is Hardware.

So maybe thinking of things this way is that a Virtual Environment is a way to Fool a Operating System into thinking that it's actually controlling something when it's not. In the case of a Dual Boot Option all the Installed OS's are actually controlling the Hardware when they are running when not in use they are shut down and not running but in a Virtual Environment all Installed OS that are started are running all of the time.

I hope that is of some assistance to help you understand. And yes I know it's as [b]Clear as Mud.[/b] :D

Col

Think of the situation in terms of Emulation.

That is at least a word that can be thought of in terms of REAL LIFE. If you were to see someone doing something that you thought was impressive or looked like being fun - you could attempt to 'emulate' their approach to the thing they were doing.

In computing terms, emulators abound (if you are interested in them and bother looking for them).

If you were to travel back in time, almost 30 years ago, computers were in their infancy as far as the domestic variety were concerned. The first domestic computers available to the average punter were things like the beasties that came out of the Sinclair factory in the UK, and the Commodore output from America.

If you were to try and play with, let alone find, a Sinclair Spectrum 48K or a Commodore 64, you might have your work cut out. You can however, run Spectrum and C64 emulators on a modern PC. Once the emulator is running, you can then load the Spectrum or C64 program into the emulator and play the game.

In terms of compatibility, you cannot run a Spectrum 48K program or a Commodore 64 program on a PC, but the emulator will allow it. So the emulator fools the program into thinking it is actually running on a Spectrum 48K or a Commodore 64.

If you were to push the program too far, or interfere with its code (using Peeks & Pokes) you would obviously damage the program, but ONLY inside the emulator - because the PC is kidding on that it is another machine.

The enxt time you start the Speccy or C64 emulator, everything is back to normal because strictly speaking neither of them actually exist - they are VIRTUAL.

The same goes for running older versions of PCs. Instead of hunting far and wide for a PC equipped with an 80286 processor so that you can fire up MS-DOS 4.2, then run a DOS program on it - you simply run VMM and create a virtual 80286-machine, complete with MS-DOS 4.2 mounted on its own virtual hard drive.

If anything goes wrong, even if you get online with it and get a virus infection, it doesn't matter - because the 80286 PC doesn't actually exist - it is also virtual, just like the Speccy or the C64.

'Virtual' is more a buzzword (and a hindrance when trying to understand it) - 'Emulator' is far easier to understand and basically exactly the same thing. :)

that each Virtual PC that you create is using up your Hard Drive space. If you allocate 1GB to a win98 Virtual PC you will lose 1GB of hard Drive space. If you install XP you will have to make a bigger Virtual Drive to accomodate it. I really dont think that you need to go down this track Paul.

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Thanks for that.

For me it was reassuring that one does have
to install the OS into the virtual computer
and also that it really uses real resources.

I cannot see an application for it, but at
least now I have an idea.

Paul