[Samba] Size of locking.tdb?

Alexey Lobanov aal at evidence-cpr.com
Thu Oct 2 08:42:23 GMT 2003


I ask you very much to help in the investigation. I could not find any documents stating 
that the Samba trivial databases must reside on sync-mounted filesystem in Linux (or any 
other OS). And I suspect that this bug (non-coherent modification of locking.tdb) is 
widespread, but many systems do not notice it, just because it does not _instantly_ kill 

The question to all of you running Samba on Linux. What is the REAL behavior of your 
locking.tdb file at async ext2 partition? Does it decrease in size while normal Samba 
operation, after the end of business hours?

Yes, I had seen reports about endless grow of this file. But we investigate other 
variants now: either stable maximum size or size decrease upon server "unloading".

Thank you.


On 1 Oct 2003 at 13:41, Gerald (Jerry) Carter wrote:

> > we never pack TDB's.  You can safely remove the
> > tdb after shutdown though.  What size are you seeing?

> Great. I know wtf.
> Linux 2.4.any, Samba 2.2.any. When TDB's reside on "async" mounted ext2 
> partition, locking.tdb size FOLLOWS the number of records. From 25 kilobytes to 
> hundreeds of kilobytes, and back. When /var is mounted "sync", the database 
> really stays at maximum size (now 548864 bytes after >3000 records at peak). 
> "use mmap" does not affect this behavior.
> It is difficult for me to say where is the exact bug resides: in Samba or in 
> Linux 2.4 kernel. But the name of bug seems to be "non-coherent access".
> It is also difficult to say now if "sync" mounting is a sufficient workaround. 
> At least, it is not fatal for performance if /var/spool and /var/log are 
> mounted separately.
> And it is funny that this TDB "packing" which definitely happens at async Linux 
> filesystem is not necessary fatal for locking database contents. Looks like in 
> this case Samba dies in quite rare set of conditions. Maybe, when the number of 
> records falls very quickly from 2000 to 50, "accounting team go home". Maybe 
> not.
> Thank you!
> Alexey
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