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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?


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>