[MisterTea]

Plan 9 implemented this concept in the worm cached file server, one of the on-disk file systems used in plan 9. The idea was you have a disk based cache and a WORM (write once, read many) dump consisting of optical juke boxes. Writes to the fs are stored in the cache until the fs is dumped to worm, manually or on a schedule (hard-coded to do this 2am every night.) http://man.9front.org/4/cwfs

The idea was to reduce the cost of storage by removing long term data from costly hard disks and storing it on cheap magneto-optical disks which like CD's could be stored in an automated juke box. Write all the data you want to the cache, then commit to worm. As the worm fills, you just buy another disk and put it in the jukebox. The history(1) command then gives you a files history as a set of paths you can bind over another path to use an old version of a file instead of copying it. Its really a file system for programmers. http://doc.cat-v.org/plan_9/4th_edition/papers/fs/

This idea was expanded on with Venti/Fossil which allows you to build file systems from arbitrary venti data sets. http://doc.cat-v.org/plan_9/4th_edition/papers/venti/