I had that particular bug tracker item open in my browser earlier today :)

However it is quite long and I did not read everything in that discussion. The topic is the difference between ext3 and ext4, particularly their features data=ordered and delayed allocation. Where does it say that not even sync, much less fsync, is adequate for ensuring your data is written to disk and reliably retrievable? The entry that you reference (45) states quite the opposite imho. On ext4 (especially when replacing files on pre-linux-2.6.30 or something like that) you must fsync() your files at the appropriate times to prevent a high risk of data loss. On ext3 it is (a bit) helpful too, though it might slow things down.

I wonder what your objective is.

I was just reading that passage in the man page (which I quoted in my original post) and was wondering how to do that in Perl.

Update: That entry 45 has a lot of common text with this blogpost, which I found quite enlightening.