Kolab2 Slapd hanging - master/slave replication issues

[Dieter Kluenter]

Hi Stephan,

Stephan Buys <list at codefusion.co.za> writes:

> Hi all,
>
> Today I'm the one in need of advice :-)
>
> We have a big Kolab2 server with about 350 users on it and 2 slave servers
> in remote geographic locations. The slave servers have between 50 and 100
> users each.

These are not large numbers, in terms of directory speaking :-)

> We deployed Kolab2 on Sunday and have since had several issues:
>
> 1) slapd keeps on hanging. I suspect that this is due to the strain taken by
> slapd as it needs to service, "uid requests", "mail routing", "sasl auth", etc.

Please give some more details
- OpenLDAP versions of master and slaves
- Contents of DB_CONFIG
- cachesize in slapd.conf
- idlecachsize in slapd.conf
- indices in slapd.conf
- database definition in slapd.conf
- BerkeleyDB version and number of patches applied

> 2) When slapd hangs we need to do a db_recover to get it back up and running.
> After having to run db_recover on the slave as well as the master servers the
> databases have now become inconsistent.

A database corruption occurs only with heavy write load and
insufficiened cache size or a flag DB_TXN_NOSYNC set in DB_CONFIG.

> So my questions:
>
> 1) What can I do to make slapd more robust? Pre-forking, more
>    children processes?

That depends on your OS and hardware as well as on the number of
connections in a given period.

> The main server is running at load average of 3 at the moment which I am sure 
> compounds the problem...
>
> 2) How easy is it to re-sync the master-slave databases? Can I stop the servers,
> copy the master dbs to the slaves and start up again?

You may slapcat the master and slapadd on the slave.

> Any tuning/optimisation tips would be greatly appreciated.

I would like to, but a few more informations would be helpful :-)

-Dieter

-- 
Dieter Klünter | Systemberatung
http://www.dkluenter.de
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