I use my Pi as a PVR. I have use Samba (SMB) to share the drive to which the recordings are being written. I've noticed that when Windows accesses this shared drive while a recording is being made and the file is growing in size, the file appears to grow in "chunks" - the size and the apparent length (time) of the recording only changes every few minutes - sometimes an update can be triggered by F5 (refresh Windows Explorer). It's not that the PVR program is only updating a header infrequently, because VLC on the Pi, accessing the file via the UNIX filesystem, can see beyond the point at which VLC on Windows thonks the file ends. It looks as if it's a Samba issue, as if Samba is buffering the contents. But it's not a restriction of SMB as a whole, because if one Windows PC accesses a file using SMB that is being written to on another Windows computer, the true up-to-the-minute size and contents are available.
Is there a parameter in Samba on Linux which avoids this or shortens the amount of lag? It's not the end of the world if there isn't a way. It just means I need to wait until a recording has finished before I can rely on being able to read the whole of the file.