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Re: Drawbacks of Berkeley DB cache settings?
--On Thursday, June 26, 2003 2:02 PM +0200 Chris van der Merwe
I'm wondering if anyone on the list is familiar with the "inner-workings"
of the BDB, specifically my question is: Does enlarging the cache of the
BDB via DB_CONFIG pose any danger of updates to the directory being lost
in the event of a powerfailure or crash? I ask because I've managed to
greatly improve the results from OpenLDAP by making some fairly large
cache settings and I'm wondering if BDB has some mechanism to prevent
corruption in the event of a crash (with a large un-processed write
My understanding of BDB is that when new changes come in, they are written
to the __db.* files. When slapd is stopped, or when the time/size of
changes limit set in slapd.conf by the "checkpoint" attribute are hit, it
will write any pending changes to the *.bdb files. After any crash, I
recommend running db_recover. If there has been corruption problems caused
by the crash, BDB will try to fix it.
As always, doing routine backups, and having a method of tracking changes
is good. We have an event system here, so if we ever have to do a Point in
Time restore, we can simply play back all the events from the time the
backup image was created. So far, I've seen very few cases where I had an
unrecoverable DB. Once was when the partition of the HD got corrupted, and
the other times were self-inflicted.
Senior Systems Administrator
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