Use F_FULLFSYNC ioctl where supported

[richard]

I've recently noticed that, when performing an fsync, sqlite and mysql use a special ioctl on OS X which makes an effort to ensure that the disk's internal write buffers are flushed to the platters. Perhaps we should be using this ioctl too.

http://lists.apple.com/archives/darwin-dev/2005/Feb/msg00072.html has some details about why this is needed.

http://www.sqlite.org/cvstrac/fileview?f=sqlite/src/os_unix.c&v=1.195 contains the sqlite implementation; search for the "full_fsync" function.

[olly]

Definitely worth considering.