[ryannielsen]

Actually, I disagree. What I describe is more like RAM buffered IO, where the space can be reclaimed at no cost, rather than swap, where the data must be saved for coherency.

It's entirely viable for a filesystem to archive all of the data you've ever created. Treat the archived files as an LRU cache and, when new data needs to be saved, just write over the least recently used data. Instead of a volume bitmap of used blocks, you have a tree that can be traversed to get the blocks that can be overwritten. This is not data that must be saved, like the swap; it's data that should be saved until something else needs it, at which point it's overwritten, like most OS's RAM IO buffers.