[Samba] Samba vs. Windows : significant difference in timestamp handling ?

f.pospischil at telenet-ag.de f.pospischil at telenet-ag.de
Mon Aug 11 15:57:40 GMT 2003

Hi there,

i still have a weird problem with Powerpoint an Excel files stored on a
Samba share.

Only read on if you
-use a samba share as MULTI-user file repository (no force_user etc.)
-where multiple, different users share files in common directories
-the modification time of a file is of any relevance to you.
(seems like lots of folks don´t bother access rights or keep their
information strictly user-wise organised ...)

Please look at the following example (Powerpoint 2000 and 2003 on
Terminalserver and Standalone)

Timestamp history (on Samba share, 2.2.8a RedHat  Linux 9  with XFS
File is initially created :
Test.ppt mtime->12:40:05, ctime->12:40:05, atime->12:40:05
File is then "viewed" (open in Powerpoint and exit without changing/saving
anything) by same user:
after file is opened:
Test.ppt mtime->12:40:05, ctime->12:40:05, atime->12:45:59
after file is closed:
Test.ppt mtime->12:40:05, ctime->12:40:05, atime->12:45:59

Hmm, looks o.k. !

Now a different user "views" the file. (Different means, his username on 
Options-dialog in any Office-Application is different.)
Can be faked by simply changing username in options-dialog in Word e.g in
the same session.

while file is open:
Test.ppt mtime->12:49:16, ctime->12:49:16, atime->12:49:16

oooops, looks like a new file ...

after file is closed:
Test.ppt mtime->12:49:16, ctime->12:49:16, atime->12:49:16

... still looks new to me !

Now the same procedure again,
same environment except the file is stored on a Windows2000 Workstation
(with NT file system tunneling disabled)

file create:
size on disk: 8.192 bytes
created  15:48:36
modified 15:48:36
accessed 15:48:36

"viewing" by the same "user"
while file is open:
size on disk: 8.192 bytes
created  15:48:36
modified 15:48:36
accessed 15:48:36

file closed:
size on disk: 8.192 bytes
created  15:48:36
modified 15:48:36
accessed 15:48:36

O.K. that´s almost the same behavior that samba shows. (Except that on
windows, the file doesn´t even look accessed)

Now change the Office-options to a different user and open the file:
While open:
size on disk: 12.288 bytes
created  15:48:36
modified 15:48:36
accessed 15:50:30

WOW! the file is bigger though it was not modified and is still the one
created 15:48:36

Now exit Powerpoint:
size on disk: 12.288 bytes
created  15:48:36
modified 15:48:36
accessed 15:50:30

... still the same.

So on windows, the file seems now to be still the same version. (created
15:48:36 last modified 15:48:36).
This is not true as Bits and Bytes are concerned but reflects the semantic
of "open a file and exit without changing anything".

On the Samba share, the file looks like "brand new information".

I think that this makes a BIG difference on a shared filesystem where the
modification time of a file serves as an indicator for the relevance of
(Would you bother a file named "Hot_News" that was last modified 2 Years 
? And would you like this file to become "really actual" by open it with 
associated application and exit without saving/changing anything ?)

I think, Powerpoint (and Excel at least) store the initial timestamp and
explicitly change them after the file is closed without "relevant" 
I suspect, the current user is written to the file so Powerpoint can
announce: "File is currently opened by XYZ. Open it read-only?" or sth. 
The application tries to hide this change by doing some "magic" on the

Question 1:
Can somebody please confirm this behavior ?

Question 2:
a) Does anybody know how the timestamp is changed (File system API, System
API, magic spell ...) and why this mechanism fails on Linux/Samba/XFS ?
(dos_filetimes parameter already set to yes)
b) How can this be debugged efficiently in Samba ? (Log level 3 delivers
tons of data, sth. like NT_STATUS not supported ... What is the meaning of
the errors ? How to isolate the relevant entries ?where to begin ?)

Question 3:
Is it possible to adjust samba to show the same behavior as NTFS ?

Any help concerning this nasty "bug" is really appreciated.
After some months of preparation for the "big move" from Windows to Samba
fileserver, this effect is a real show-stopper as most of the users rely 
the modification time for syncing information with Laptops, handhelds,
project-lists and between each other.

Frank Pospischil
Leiter IT
Telenet AG Rhein-Main

Marburger Straße 14
64289 Darmstadt

Tel.: +49 6151 733-353
Fax.: +49 6151 733-325
Web: http://www.telenet-ag.de

P.S.: Leser der deutschen Newsgroup de.comp.os.... mögen mir bitte die
englische Variante verzeihen. Ist doch ein bisschen aufwändig das nochmal 
deutsch zu schreiben ...

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