[Samba] File growth behavior of Mac OS X and WinXP

[Jeremy Allison]

On Tue, Dec 21, 2004 at 01:09:59PM -0500, Victor Moran wrote:
> Hello List,
> 
> I've searched the internet and I haven't been able to figure this out.
> I hope someone here can point me in the right direction.
> 
> I have a MacOSX 10.3 machine and a WinXP machine that are being used to
> produce large video clips (@1gig).  After they are rendered and ready
> for playback, they are copied to the playout machines using a system
> that uses watch folders shared out over samba.
> 
> The watch folder works based on file size.  For example, 40 seconds
> after a file's filesize stops growing, the system assumes the file is
> complete and starts moving the file onto the playout device.
> 
> The problem I've found is that windows xp and mac osx (10.3 at least)
> both cause samba to allocate the entire file size at the start of the
> transfer.  For large files this causes a problem since the file is not
> finished writing to the smb share when the playout transfer system
> takes the file and tries to move it and then delete it.
> 
> Any help on how to change OSX and WinXP's behavior or how to keep samba
> from allocating disk space at the start of a write would be very
> appreciated.

If the client writes at the end of the file, and then fills in the gaps
then there is nothing we can do to fix this in Samba. Who wrote the watch
system ? Pre-allocating a known filesize by writing at the end then filling
in the blank is a common idiom in file transfers, I would expect a watch
system to deal with this.

Jeremy.