[mythtv-users] Use of fsync

[Raymond Wagner]

On 10/22/2013 11:18 AM, Rich Freeman wrote:
> Does anybody know why MythTV uses fsync to force writes to disk when
> recording (in ThreadedFileWriter)?
>
> I just noticed that some of my recent recordings were getting
> truncated (a recent behavior change - though I can see why it might
> not be a bad strategy).  The use of fsync on a fairly busy drive
> basically kills drive throughput and as a result the buffers overflow.

With the default Linux IO scheduler, if you allow a large volume of 
writes to build up, eventually Linux will panic and block all IO while 
it flushes out the whole cache.  It's nothing to do with preventing data 
loss in a crash, but a manipulation of the system to prevent poor behavior.