slapd does not answer in time

[Hans Moser <hans.moser@ofd-sth.niedersachsen.de>]

Hi!

I have a 4 cpu machine with SLES 9 and OpenLDAP 2.3.35.
This is master to about 65 slaves via syncreplication.

These slave were set up subsequently without any problem. In the last 
time every now and then the master cannot answer searches in time. 
Clients time out - i.e. Postfix doing address verification. This may 
have to do with writes to the master and the replication.
The worst time was, when I had to reinitialize about 15 to 20 slaves and 
these slave checked the master to get in sync.* Other clients got no 
answer for a long long time. :(

The iron is idle. Load average is 0.00.
There were limiting factors like file number etc, which limited process 
numbers, but this was solved in the mean time.

Which number of connections to the master does a replication slave open?

How can I find out, what is limiting slapd and keep him from responding 
in time? Log files does not give me a hint, but I don't really know what 
to search for.

* I take a "top level" ldif file to start the server up - ou=bla,o=foo, 
ou=log,ou=bla,o=foo and ou=humans,ou=bla,o=foo -
and the latest hourly branch dump (these slave only replicate one branch 
from the master server) - ou=humans,ou=bla,o=foo - from the master to 
fill the server. In this case the slave contains all the data, but 
checks ALL entries to be "up to date". Is there a way to prevent this? 
The slave does only have to check for changes that happened in the last 
hour (since the dump).


Hans