DragonFly kernel List (threaded) for 2003-09
Re: Ridiculous idea: Cache as ramdisk?
:Hm, my only suggestion is to abstract it just a little further - say
:every file has a different "importance" - from (say) 0 for "not
:important at all, I don't care if it suddenly disappears" to (say) 9 for
:"very important, make sure it's in NV storage ASAP"
:This way the behaviour isn't tied to any particular mechanism, and that
:should theoretically make it easier for both implementers (who can use a
:different mechanism, should it come down to that) and users (who don't
:have to think in terms of "buffer cache" and other concepts they don't
:necessarily understand well.)
"Ick". This brings non-deterministic behavior to a new level :-).
It may sound good on paper, but it will never work in practice because
in practice there are only two levels of importance: (1) You don't
care if it goes away, or (2) It had better not go away.
:Journalling file systems seem to be rather optimized for recovery, vs
:the impression I get when I hear the word "journalling" - I think of
:something more like CVS, where you can get any older version of a file
:merely by requesting a different tag. Such a "write once" filesystem
:would be very nice to use, I think.
:Anyway... back to your regularly scheduled BSD forking...
:-Chris (in Vancouver, if you care)
There are major advantages to being able to access a filesystem
as of some date in the past. For example, it makes 'undelete' work
very precisely. Another huge advantage to a properly journaled
filesystem is that one can run a continuously streaming 'incremental
backup' of the filesystem as well as use such a stream to maintain a
fully independant off-site copy of the filesystem in near real time.