Note that we already have file system snapshots for ffs file systems, see fss(4). They are used for backup purposes (atomically create a snapshot, while the file system is busy, then backup the now quiet snapshot) - among others.
> *) > What is it good for? The only practical use I can imagine are backups on > thin clients, which operate without a hard disk. But this is clearly > far-fetched, in my eyes. I have no clue. For the disklaess (or r/o flash based) thin clients you probably can easily do something easier at application level (like: mount flash r/w, copy some files over). Martin