Hello,

We have a openldap (2.3.30, debian etch version 32bits) with 4 nodes (xen vm with one cpu core, Intel Xeon 3.20GHz and 2GB of RAM). It that farm we have two databases one with 121K entries (for authenticating users, with lots of connections) and other with 40K entries (with public information of our students, for example).

Now we have migrated to two openldap (2.4.21, ubuntu lucid 64btis) farms. One with 4 nodes (xen vm with two cpu cores, Xeon E5450 3GHz, 2 GB of RAM) for the authentication database, and other with 2 nodes (with the same resources than the other) for the other database.

The problem is that in the authentication farm we are having lot of problems due to heavy load, although we are not completely migrate all clients to this new farm (we already have clients querying the old farm), but in the old farm we didn't have any problem (just some punctual problems long time ago).

The only difference between the old and the new farm is that the old farm was replicating information with slurpd. The new one is a multimaster configuration. The configuration of the replica is:

mirrormode on syncrepl rid=11 provider="ldap://<server1>.um.es" binddn="<replica user dn>" bindmethod=simple credentials=<creds> searchbase="<base of database>" type=refreshAndPersist interval=00:00:00:10 retry="5 5 300 +" timeout=1

syncrepl rid=12 provider="ldap://<server2>.um.es" binddn="<replica user dn>" bindmethod=simple credentials=<creds> searchbase="<base of database>" type=refreshAndPersist interval=00:00:00:10 retry="5 5 300 +" timeout=1

syncrepl rid=13 provider="ldap://<server3>.um.es" binddn="<replica user dn>" bindmethod=simple credentials=<creds> searchbase="<base of database>" type=refreshAndPersist interval=00:00:00:10 retry="5 5 300 +" timeout=1

syncrepl rid=14 provider="ldap://<server4>.um.es" binddn="<replica user dn>" bindmethod=simple credentials=<creds> searchbase="<base of database>" type=refreshAndPersist interval=00:00:00:10 retry="5 5 300 +" timeout=1

This configuration is in the 4 farm nodes. We have checked indexes and both farms have the same.

Another difference is that authentication database entries have some attributes obtained from the other database via dynlist overlay. In the old farm, because the two databases are in the same server we had no problem, but in the new one we have to configure this database as an ldap proxy to the other farm, with cache overlay used in this.

Heavy loads appears randomly in all nodes (not always with all nodes at the same time). When this happens, slapd is using 100% (well... top reports 200% because we have two cpus), there is no swap, no iowait....

Any idea of what could it be the problem? Is this multimaster configuration so heavy load?