Re: OpenLDAP, bdb and Linux filesystems

["Jong" <jongchoi@OpenLDAP.org>]

> Hi,
> 
> we actually did the tests in an real life environment that was setup
> rather straightforward because we didn'3t expect any problems in advance.
> 
> The database was located on a IDE-harddisc and we did store the BDB logs
> on the same partition as the BDB data (and the Journal for the
> journaling filesystems). I know that we might improve performance by
> moving the logs to another drive, but I guess this should apply for all
> the setups.
> 
> The import took approximately 1 min 10 seconds on ext2, 1 min 40 on XFS,
> 4 min 10 on reiserfs and 4 min 30 on ext3. The CPU was idle all the time
> and the subversion process was mainly in the D state (meaning
> uninterrupible sleep (wait for IO)) while waiting for the completition
> of a sync-call.

The ext3-users mailing list had a related discussion thread between ext3
and bogofilter which also uses Berkeley DB.
(http://www.redhat.com/archives/ext3-users/2003-February/msg00000.html)
The cause of the problem turned out that the application is making a set of pages
repeatedly dirty when ext3 has already scheduled IO for the same pages.
This seems to lead frequent blocking described above.
Eitehr increase the BDB cache size, or tweak several ext3 paramaters as
suggested in the above discussion thread (changing commit interval or journaling mode).
- Jong
 
> I know that this setup wasn't perfectly tuned, but that is what most
> people do (and the speed improvment for moving the logs to another
> spindle should also be there for ext2)
> 
> Yours
> Stephan Siano
> 
> - --
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> Dr. Stephan Siano, Consultant
> SUSE LINUX AG, Mergenthalerallee 45-47, D-65760 Eschborn
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> F: +49 (0) 6196 409607    - stephan.siano@suse.com
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