> what about a "CVS" or "Subversion" system?

I think there are a number of different objectives for what often is called
"backup" which are to be solved efficiently by different tools, usually.

1- quick and complete system restore (often to a different disk or
partition) in case of disk failure (RAID is probably the most user-friendly
for this one)

2- quick and complete system restore in case of a bigger thing like a fire
in the office (needs off-site storage of the above, therefore some media --
which could be one disk of a RAID array that gets exchanged once a day)

3- quick and complete system restore in case of user or system error
(usually to the same disk or partition, just going back in time a bit --
RAID wouldn't help here, this needs an actual backup and therefore a method
for rotating the media, or unlimited budget)

4- archiving of files that are not needed frequently (doesn't usually have
to be quick, as it supposedly is not a frequent thing, and can even be
spread over different media -- which shouldn't be the case with the methods
above --, as long as they are properly catalogued)

5- version control of files with which people work (that's the cvs thing --
very useful, but not quite a possibility for the whole system -- and the
version control repository itself needs backup through the former methods)

Having all that integrated in a file system doesn't seem to be impossible
with today's hardware capabilities and prices. From what the mainframe
people say, something like that has already been done.

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