> One point that I no longer recall the reasoning behind is that xlog.c
> doesn't think O_SYNC is a preferable default over fsync.
For larger (>8k) transactions O_SYNC|O_DIRECT is only good with the recent
pending patch to group WAL writes together. The fsync method gives the OS a
chance to do the grouping. (Of course it does not matter if you have small
tx < 8k WAL)
Andreas