Re: bdb backend: memp_trickle

[Eric Irrgang <erici@motown.cc.utexas.edu>]

On Tue, 15 Feb 2005, Quanah Gibson-Mount wrote:

>> I'm using OpenLDAP 2.2.23 and Berkeley DB 4.3.27.
>
>Okay, I strongly suggest not using BDB 4.3 with OpenLDAP 2.2.

I notice you've made that suggestion before but can't find the original
post.  You've said that the logging is broken?  Are there fundamental
problems with db4.3 or is it just some bugs that are likely to get fixed
in upcoming releases?  Is it a big enough issue that someone should fix
the 2.2.x sources so that the configure script doesn't looke for db4.3
first?

>hdb certainly is not abandoned... It is actively maintained.  No idea why
>the man page isn't there.

Yeah, I was surprised to notice the source code seemingly up to date.  I
guess the man page got lost...  I don't feel like prowling CVS right
now...

>It configures the same as back-bdb.  If you have back-bdb configured
>already, and you want to try hdb, slapcat, clean up the old db, change
>slapd.conf to read "database hdb", slapadd.

"Okay, but what does it DO?"  I guess I need to just look through that
code after all.  I'm curious as to what it does to reduce writes.  I
normally get drastically improved throughput just by using mp_mmapsize
large enough to map all of my database and indexes into process space and
checkpointing infrequently, but sooner or later that data has got to go to
disk, and I'd rather it didn't happen all at once.

Here's another thought for the BDB brains out there: any reason not to
issue a db_checkpoint from the command line while slapd is running?  From
what I can tell, db4 is meant for this type of concurrent activity.  I
tried it for grins and it seemed to work fine (afterwards slapd was able
to shut down almost immediately because it had nothing left to flush), but
it creeped me out and I'm reluctant to make a habit of it.  :)

-- 
Eric Irrgang - UT Austin ITS Unix Systems - (512)475-9342