This may be a crazy idea, but in case it isn't...

'Live' CD distributions like Knoppix use UnionFS to allow a read-only image from CD to be made 'writable' by overlaying a ram-based filesystem.

So how about doing offering something similar using those distro images? give the customer the option to mount the distro image r/o, and his/her disk space as a r/w overlay on top? then the only disk space consumed from the customer's allocation would be things we'd modified (packages we installed or upgraded, configuration files we edited, etc.)

That raises many questions, like are distro images ever updated with security fixes, etc. I'm also guessing that currently the distro images are not present on every machine, perhaps only one or two copies per data center. And UnionFS hasn't quite made it into the mainstream kernel yet (though it's in Andrew Morton's -mm tree, so it's on its way).

I'd like to see UnionFS offered, even without the ability to use the distro images. I could understand if Chris wanted to wait until it hits the mainline kernel, though.

Paul