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

[Victor Moran]

Jeremy,

Thanks for your response.  Your right, the watch system is missing the
ability to deal with files that are written from the end and then
filled.  It was developed in-house.  I was hoping to find a way to
deal with this missing feature, without asking for new code since the
development group is overworked.  I'll stop looking now, I think your
response counts as hearing it from the horses' mouth.  :)

Thanks again for your response and for all your work on Samba.

Victor.





On Tue, 21 Dec 2004 10:23:42 -0800, Jeremy Allison <jra at samba.org> wrote:
> 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.
>