Basic virtualization questions

Excuse me for my lack of knowledge but I am really new to the Virtual world and have a few questions.

I work for a small charity who specialise in providing basic IT training. We have recently acquired a few Dell Poweredge 2650 ser开发者_开发百科vers and Dell desktops and we wish to offer both XP, Windows 7, Mac and Ubuntu training. I am looking at setting up a Virtual environment so that we can have a standard image for each OS (I currently use image files but it currently takes approximately 25mins to build each machine and multi-boot is not an option as the new machines have 20Gb disks).

The servers are all dual processor and we can purchase more memory(I need to justify the cost)

1. What are the memory requirements for the Host?
2. How many VM's can I run per server?
3. Can I run multiple instances of the same VM

Thanks in advance for your knowledge.

Darryn

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You might be able to get away with a multi-boot option with those 20 gig disks; each OS will probably take no more than ten gigs for minimal installs, two OSes per machine isn't terrible. (Incidentally, look around for a group like FreeGeek in your area -- larger hard drives ought to be cheap for small sizes like 120-500 gigs.)

That said, virtualization might be just what you need, if you have a handful of pretty powerful machines.

I think between one and two gigabytes of host memory for every guest VM that you want to run would be very useful. At least in my experience, an Ubuntu image I gave 1024 megabytes to ran very quickly, but I didn't press it very far. Running Firefox or OpenOffice inside the VM would probably dictate more memory very quickly. Chrome seemed snappy.

So, if you've got 12 gigabytes of RAM, you might be able to get between four and twenty virtual machines hosted on the machine simultaneously, depending upon what your guests are doing.

As for disk space, if you use QEMU's -snapshot option, you ought to be able to save disk space. Each user could boot the same underlying disk image, but their own modifications would go into the 'snapshot' file. (I have no experience trying to do long-term system maintenance with this option, so it could be that all twenty of your users need to store service pack 2 contents when they upgrade in the future; I'd be scared of trying to modify the shared disk image once you've got snapshots of it running. Perhaps having everyone store 'personal documents' and the like in CIFS shares would make a ton of sense.)

The biggest hurdle will probably be Mac; because the Apple terms of service forbid running OS X on non-Apple hardware, you'll have to have some Apple machines around to run VirtualBox.