Re: LDBM verse BDM

[Frank Swasey <Frank.Swasey@uvm.edu>]

Today at 10:07am, Kent L. Nasveschuk wrote:

> 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?

I would recommend:

1) shutdown the slapd
2) slapcat the db out to an ldif file
3) make any edits required (if you are changing from 2.0 to 2.1 or 2.2)
for schema checking to work
4) upgrade your openldap software
5) slapadd the db back in
6) chown the db files to the correct user
7) start slapd

>
> 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).
>

-- 
Frank Swasey                    | http://www.uvm.edu/~fcs
Systems Programmer              | Always remember: You are UNIQUE,
University of Vermont           |    just like everyone else.
        === God bless all inhabitants of your planet ===