I wrote:
>> strace'ing syslogd on my HPUX box shows that it doesn't issue explicit
>> fsync calls either, but I don't know of any way to tell whether it's got
>> the log files opened O_SYNC.
It occurred to me to SIGHUP syslogd and watch it reopen its log files
with strace. No O_SYNC.
So it seems fairly likely that the fsync-by-default business is indeed
a Linux-ism not shared by other Unixen.
regards, tom lane