Re: LDBM verse BDM

["Michael J. Erdely" <mjerdely@unicon.net>]

Thank you everyone for the great feedback!

-Michael


Matthew Hardin wrote:
> There's one thing to add:
>
> In the thread below there seemed to be a lack of distinction between
> back-ldbm configured to use Berkeley DB and back-bdb. The former gives you
> little more than back-ldbm with the gdbm (or equivalent) database did
> (little fault tolerance, concurrency problems, etc). The latter uses the
> transactional support provided by Berkeley DB and has more features than I
> can adequately describe here. Suffice it to say that we (Symas) never
> recommend the use of back-ldbm to our customers for production environments.
>
> Use the following search terms in Google to get more information on tuning:
>
> OpenLDAP faq Tuning
>
> Also, Quanah Gibson-Mount posted some excellent information that describes
> Stanford's experience with back-bdb.
>
> Hope this helps...
>
> Matthew Hardin
> Symas Corporation
> Packaged, certified, and supported LDAP software:
> http://www.symas.net/download
>
>
>
> > -----Original Message-----
> > From: owner-openldap-software@OpenLDAP.org [mailto:owner-openldap-
> > software@OpenLDAP.org] On Behalf Of Kent L. Nasveschuk
> > Sent: Friday, April 02, 2004 7:07 AM
> > To: Frank Swasey
> > Cc: OPENLDAP
> > Subject: Re: LDBM verse BDM
> >
> > Hello Frank,
> >
> > Just a couple questions regarding, going from ldbm to bdb since bdb
> > seems to be the a much better backend for OpenLDAP.
> >
> > I've got 4 OpenLDAP servers 2.1.23 (1 master 3 slaves) with ldbm
> > backend. If I were to upgrade one at a time any suggestions on how to
> > proceed with this? A server that went down in the past, I shutdown
> > slapd, copied the db files to the new installations and restarted slapd
> > and slurpd. I can't do a direct copy of files with different DB
> > backends. Use slapcat on the master then ldapadd on the new machine?
> >
> > Thanks
> >
> > On Fri, 2004-04-02 at 07:59, Frank Swasey wrote:
> >
> > > On Thu, 1 Apr 2004 at 3:55pm, Michael J. Erdely wrote:
> > >
> > >
> > > > Is there a convincing reason to go use a dbm backend instead of ldbm?
> > >
> > > Yes, there are several.
> > >
> > > 1) ldbm is not receiving much (if any) development.
> > >
> > > 2) ldbm has a single lock, so if you can get yourself into a situation
> > > where the whole server becomes unresponsive for an extended period of
> > > time.  For example, you fire off a search based on a non-indexed
> > > attribute that takes a long time.  Someone else asks to modify an
> > > attribute.  Their modify is stuck behind your search and any other
> > > searches that try to start are now stuck behind their modify.  Several
> > > times before I switched to back-bdb, I had to recycle the servers
> > > because things were not working.  I haven't had a single one of those
> > > deadlock situations since converting to back-bdb.
> > >
> > > 3) ldbm does not allow slapd to be up and running while performing a
> > > slapcat (bdb does).
> > >
> > >
> > > > It seems that the ldbm backend is much easier to setup.
> > >
> > > That's true.  However, it's kind of like saying an automatic
> > > transmission is easier to drive than a manual transmission.  There are
> > > trade-offs.  You'll get better gas mileage with a manual transmission
> > > once you have learned how to properly operate it.
> > >
> > >
> > > > I'm running OpenLDAP version 2.1.25 on Redhat Enterprise 3 and plan on
> > > > supporting about 30k-50k users with about 6-9 indices.
> > >
> > > I would suggest that you upgrade to 2.1.29 (there were some interesting
> > > features in 2.1.25 [as I recall -- but they may only be related to bdb]
> > > that have been fixed in 2.1.27 and beyond).
> > >
> > >
> > > > With the ldbm backend, does anyone have any good equations to
> >
> > determine the
> >
> > > > "cachesize" and "dbcachesize" settings?
> > >
> > > I do not.
> > >
> > >
> > > > I have only 512 MB of memory but plan on ramping that up to 2 to 4 GB.
> > >
> > > For the size database you are running 4GB would be plenty for a well
> > > tuned back-bdb installation.  I am running several 2.1.27 servers.  I
> > > have a couple on RH9 with 2GB of memory and a couple more on RHEL3 with
> > > 4GB of memory and they're all running back-bdb.
> > >
> > > I don't recommend RH9 (unless you also upgrade cyrus-sasl due to bugs in
> > > the version RH shipped -- I have to recycle saslauthd once a week).
> >
> > --
> > Kent L. Nasveschuk <kent@wareham.k12.ma.us>

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