RE: OpenLDAP, bdb and Linux filesystems

["Howard Chu" <hyc@symas.com>]

> -----Original Message-----
> From: Jong [mailto: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 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

With the BDB cache living in mmap'd files by default, increasing the BDB
cache size may not help very much. This may be an argument for using shared
memory instead, in these cases. You can try this in OpenLDAP 2.2, see the
"shm_key" config keyword for back-bdb.

  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support