I'm interested in exactly this up, now let me explain what would like to do with this. I'm preparing to buy 32GB of RAM and already have Quad Core. My idea is to implement another option in GRUB that will do exactly this:

1. On boot move whole / partition to ramfs, and boot ubuntu from there


2. From time to time and also at shutdown signal, run rsync to "backup" data to HDD, of course in background.

I already have SSD, and I think that rsync wouldn't take much to sync files. And also, loss of data is less important, except if it would be loss of more than 30 minutes active work, Because uptime of my computer is almost 99.99%, never turning off, so really don't think that this could get some bigger problem than forced power off from HDD.

/ filesystem is not much big, around 7GB.

Now my question is: Would this idea be "cost effective", would rsync take much resources, and is somewhere already implemented some similar solution of this?