Fsync, sync: does it really do what it should?

Question

I would like more clarification on the functionality of the sync (8) and fsync functions on Linux (2.6.31). Does the file check for appropriate storage?

Answer 1

http://linux.die.net/man/8/sync

It does not guarantee that files will be written to the appropriate storage. This only ensures that cached / buffered data is flushed to the disk device. It doesn't matter if it is an SD card or something else.