Posted Mar 17, 2009 15:56 UTC (Tue) by ssam (subscriber, #46587)
Parent article: Better than POSIX?
what seems unanswered is if you can overwrite an existing file, in such a way that you either have the old or the new version, without forcing the physical write to disk.
i think a lot of people are willing to risk recent changes to a file to get performance gains and and power saving. but no one wants to risk completely loosing a file just because you wrote to it recently.
in the sequence
1) open foo.new
2) write to foo.new
3) close foo.new
4) move foo.new to foo
all that needs to happen is that the 4 does not hit the disk before 2 has.
it seems that 2 gets delayed, because that gives performance/powerusage gains, but 4 happens quickly.