fsync(2) manual and hdd write caching

[Ivan Voras]

On 10/26/10 23:36, Alexander Best wrote:
> hi there,
>
> since there's a thread on freebsd-questions@ concerning fsync(2) and the fact
> that hdd write caching can cause this syscall to basically be a no op, could
> somebody please copy the BUGS section from sync(2) to fsync(2)?

I don't think they are the same.

The "buffers" of sync(2) are not those from the discussion on fsync(2) 
safety. Or more correctly, they are but those 2 calls work on a 
different scope.

fsync(2) actually does behave as advertised, "auses all modified data 
and attributes of fd to be moved to a permanent storage device". It is 
the problem of the "permanent storage device" if it caches this data 
further.