Help me understand Virtualisation

[Nate--IRL--]

Would I be correct in assuming that if I have a dual boot XP / Vista setup, I can't have these two existing installs running concurrently, sharing the same hardware?

The only way two OSs can run is by using a Virtual machine (basically a PC emulator) inside an existing running OS?

What would be the typical use of such virtual machines? Is it possible to save the state of these Virtual machines, so it doesn't revert to a clean windows install everytime?

I'll have more questions as soon as i think them up

Nate

Edit:- I would have to install windows for each VM i wish to use, correct? I couldn't just use my current Vista intall without messing it up, right?

 

[Ben643]

Would I be correct in assuming that if I have a dual boot XP / Vista setup, I can't have these two existing installs running concurrently, sharing the same hardware?

The only way two OSs can run is by using a Virtual machine (basically a PC emulator) inside an existing running OS?

What would be the typical use of such virtual machines? Is it possible to save the state of these Virtual machines, so it doesn't revert to a clean windows install everytime?

I'll have more questions as soon as i think them up

Nate

Edit:- I would have to install windows for each VM i wish to use, correct? I couldn't just use my current Vista intall without messing it up, right?

Yep, you'll need virtual machines to have them running concurrently.

All the virtualization software I've used saves state automatically. It acts just like a real pc so when you shut it down it'll save everything to the hard drive (which will be a file saved on your pc acting as a hard drive). Also with VMware it's quite easy to make clones of the virtual PC.

I'm not 100% on the last question there may be a way to do it, but it'd be far easier just installing windows again on the virtual machines.

I'm assuming you've got enough power to run these concurrently too?

 

[Ben643]

Edit - Oops, double post. Can someone delete this.

 

[atomiser]

there are several tools to do whats called p2v (physical to virtual) conversions...which is really handy in proper enterprise environments where it might have taken several hours and/or perhaps an external consultant to put an application server in... or if you dont even have the software anymore etc... (that never happens, lol! ) but if this is only for home use i would say just install fresh into your vm. then, when you have done it, take a copy of the folder where the virtual disk is stored and keep it safe. this way, you can start from scratch again very quickly if you need to. that, or run multiple concurrent versions by simply copying the directory back to a new directory where you live stuff is stored and then simply pointing a new vm with the same 'hardware' specs to it.

 

[.walls]

there are several tools to do whats called p2v (physical to virtual) conversions...which is really handy in proper enterprise environments where it might have taken several hours and/or perhaps an external consultant to put an application server in... or if you dont even have the software anymore etc... (that never happens, lol! ) but if this is only for home use i would say just install fresh into your vm. then, when you have done it, take a copy of the folder where the virtual disk is stored and keep it safe. this way, you can start from scratch again very quickly if you need to. that, or run multiple concurrent versions by simply copying the directory back to a new directory where you live stuff is stored and then simply pointing a new vm with the same 'hardware' specs to it.

This may be slightly irellevant... but I think it will help answer the original question of "Help me understand Virtualisation"...

VMs are fantastic for both enterprise environments and testing purposes. Low load machines can easily be consolidated to a single physical host (and thereby reducing cost substantially).

For example - consolidation: I have (not personally, but look after) about 200 guests running off 10 Dell PE6850s in a test environment, about the same on a combination of servers ranging from PE2950s to R900s in a heavily reduced "mirror" of our live environment and about 40 virtual machines in our live environment.

Also, with some of the "toys" you get from VMware, you can move guests on the fly between hardware to reduce load on the hosts, increasing performance for other guests.
There are a host of other reasons - including easier backups, management, etc, etc.