Define virtualisation?

[theeldergeek]

In a nutshell, is virtualisation a case of you have a server, on which you install an OS (Server 2003 for example) and then you install something like VM Ware into which you 'virtualise' several instances of an OS (i.e. Windows XP) and then within those OS's, you run the various applications and services on your network?

Would that describe virtualisation in a nutshell? I know it's a bit more complicated than that in terms of hardware etc, and if anyone cares to expand (but keeping it simple!) I'd appreciate it.

(note: I did ask about this before, but didn't want to resurrect an old thread which had started to get a little 'complex'.)

[tmcd35]

My business manager likes to think of virtualisation in terms of 'boxes'. The physical server he can touch is 1 really big box. And inside that big box there are loads of really small boxes, that he can't touch.

Needless to say that I do a lot of nodding and smiling

Virtualisation is basically making one physical server appear and behave like multiple individual servers (or desktops).

[hotwired007]

BASICALLY:

Server(Phyiscal Hardware)<>Hypervisor(Software)<>Virtual Server(Software)<>OS(ie Server2003/2008etc)(Software)

Depending on how much physical memory you have depends on how many virtual machines you can run without it impeding on everything else.

Also depending on which server you use use you can install a bare-metal hypervisor (eg vmware ESX/i) - something i'd recommend...

[hotwired007]

Virtualisation is basically making one physical server appear and behave like multiple individual servers (or desktops).

OR a way of running multiple software servers from one box... its only software... like running 20 copies of internet explorer... just more complex

[vikpaw]

What you said is essentially correct @theeldergeek; the best way to get your head around it is to try it.

the main (physical host) machine doesn't have to be a server - you could install vmware server / vmware fusion on a desktop pc / mac.

You can take whichever system of virtualisation you choose, and create a 'virtual machine' and do what you like with it. install an OS, play at the cmd prompt. add and remove 'virtual' hardware. all of these resources are really areas of your host computer, e.g. the virtual hard disk is just a file on your computer that is treated like it's a real hard disk by the virtual machine.

basically it's like an emulator and will feel very much like you are using remote desktop, but with the added advantage of having a network KVM, in that you can see the bios screen and basically the console itself, whereas remote desktop terminates when you log off.

the thing is, with hyper visors / bare metal installs, you don't even need to have an OS on your host machine be it server or desktop, it can be purely dedicated to virtualisation and have it's own cut down OS, i.e. VMWare Esx is linux based, Windows Hyper-V has a cutdown version of Windows with no extra features added.

As above post, it is just like having lots of bits of software running, so if your host has lots of diskspace and memory you can have any number of virtual machines inside it. Say for instance they are servers which is the common usage. Once they are set up, you can treat them as real. Put them on the network/domain, add other software, create services. Do what you want basically. No one else on the network would be any the wiser. The only time it's apparent that they are virtual is when you need to shut it down and restart, because there's no button to press, you need to use the software. If you want to change hardware, again, it's a software function to go in and extend the size of a harddisk. That's what makes it powerful.

Hope that helps.

[djm968]

Bare Metal Virtualisation which is the now the norm, is essentially like 3 layers. The 1st layer being the physical hardware (Server) The 2nd layer the software hypervisor (VMware, XenServer, HyperV) and the 3rd layer which consists of all of the virtual machines (operating systems) that sit on top of the other two layers. It is the hypervisor and management software that does the clever stuff like load balancing etc.

[powdarrmonkey]

Are you after a quotable phrase? Virtualisation is the consolidation of multiple physical machines (of whatever purpose) into one which maintains segregation but divides resources up based on time and demand.

[jamesfed]

'A virtual host is a physical server/PC that allows multiple virtual machines (which can be anything from Windows XP, Server 2008 to Linux) to run at the same time on a single piece of hardware to gain a variety of advantages ranging from improved stability (by separating out services) to lower power consumption (and so cost savings).'

[penfold]

Server virtualisation is the process of encapsulating one or more complete server operating systems, and their applications, within a virtualised environment on a host server. These virtual servers are separated from the physical hardware on which they live by a virtualisation layer.

In a nutshell it allows:

Lower maintenance costs because of a lower number of physical servers
Allows the host server to schedule and allocate resources such as CPU cycles, memory and disk space between the virtual servers
Introduces the possibility of migrating a complete virtual server between physical hosts
You can deploy multiple operating system technologies on a single hardware platform(Windows 2003/2008, Linux etc)

[powdarrmonkey]

Server virtualisation is the process of encapsulating ...

Please at least have the decency to acknowledge your sources.

[jamesb]

Virtualisation is fundamentally very simple. It's using software to emulate physical devices. Whether that's a server, router, network cabling or anything else.

Technically the old console software emulators are virtualised environments.

It gets complicated when you get into host systems, as they can be a workstation, single server, collection of servers, fully equipped datacentre or any other configuration of hardware you might care to name. In theory the host environment is irrelevant if you're only considering the virtualisation side of things, and there's no need to get too wrapped up in the details unless that's what you're trying to find out about..

[theeldergeek]

Are you after a quotable phrase? Virtualisation is the consolidation of multiple physical machines (of whatever purpose) into one which maintains segregation but divides resources up based on time and demand.

Yee gads no, but thanks anyway

No, I'm just trying to understand the process behind it all a little better, with the aim of being able to take a few strides forward into the technology in the very near future.

Some of the comments have been very useful - nay, they have all been useful, but those I understood more useful than others

[tmcd35]

I think the trick to understanding virtualisation is to jump in at the deep and and play with it. Here's a task for you, by the end of it you should understand virtualisation.

Download and install a copy of Virtualbox onto your highest spec PC you can 'play' with. Download a Ubuntu linux iso. Now run Virtualbox and create three virtual computers inside Virtualbox. Give the three PC's different specs - say PC1 (1 CPU, 512mb, 20Gb HDD), PC2 (1 CPU, 256mb, 40Gb HDD), PC3 (2 CPU, 768mb, 15Gb HDD). Now install Ubuntu on to each of the three virtual computers and make sure they each have internet access. Now try running all three at the same time. Then create a shared folder on 1 of the virtual PC's and access it from one of the others.

If you can do all of that you'll gain a fair grasp of what virtualisation is, how it works and why it is useful.

If you have a technet subscription or some spare copies of Windows then you can use Windows instead of Ubuntu (or if yo have another favourite distro then use that, or mix and match - try PC1 Ubuntu, PC2 XP, PC3 Win7). I just choose ubuntu (and Virtualbox) to keep things free and easily available from the internet.

Good luck

[penfold]

Please at least have the decency to acknowledge your sources.

I dont know - was a group project where we had to do a presentation a while back and dragged this up from a slide. And it wasn't from your link, but apologises if it offended.