Comment 3 for bug 20717

In the early days, "sync" was indeed the default, but we switched it to async;
please see:

  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=309591;archive=yes

sync is the wrong mode for flash devices due to exaggerated flash wearout, and
it is a very inconvenient mode for hard disks since it slows down writing by the
factor 10 or even worse.

I won't change that back since the reasoning in #309591 was really sane.

About FAT and sync: the option works halfway. The write lag is much smaller than
in async mode, but after a completed write operation there are still unwritten
things in the cache.