on suse, I was using sync in the fstab entry for the vfat fs for my hotplug devices, like memory key.

It was slow, but I believe all my data was actually written to the device by the time my write was complete, and no data was still cached.

Then found out about the flush option (http://git.kernel.org/?p=linux/kerne...f195d7347ce3e4) and its much faster, and most of the data seems to be written to the device but there is no guarantee its done when my write completes. Does anyone know if I am guaranteed if all the data is written to the device by the time I close the file I am writing?

Basically the concern is with flush, when I would get back any kind of i/o error if there is a problem comitting the data to the media? By flie close, or not till unmount if then ...?