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Re: ldap load measuring and reproduction tools

--On Sunday, March 13, 2005 10:32 AM +0100 "J.Smith" <temp201@hotmail.com> wrote:

The current plans are to add a total of about 10 to 20 ldap replicas to
master.  However, this raised some questions. For example, there might be
a real world practical limit (or even theoretical limits) to the amount of
replica's you can add to a master server. Another concern is that the
might be spending all of its time synchronizing the replica's, without
able to answer any request/updates any more, or will at the least require
significant hardware upgrades.

You really leave out a lot of information that might be helpful.

1) How many entries are in your poorly designed tree? :P
2) What version of OpenLDAP are you using?
3) What database backend are you using in slapd.conf?
4) What database software are you using behind it?


Stanford has 9 replica's, running OpenLDAP 2.2.23 with the bdb database on Solaris 8 running on a SPARC based SunFire v120, using Berkeley BDB 4.2.52 + patches as its backend. slapd has a 20k entry cache, with a 20k idlcache. BDB is configured to have a 2GB memory based cache.

3 of our replica's are dedicated entirely to serving our email query needs, and together serve about 1 million BINDs a day just for that purpose. SEARCH amount is somewhat higher than that, since some binds perform multiple searches. OpenLDAP is resilient enough that I can shut down 2 of those 3 servers, and still meet the load needed to sustain that bind rate without the server breaking a sweat.

The other 6 serve general campus queries, and don't do so much, because that load is much lighter.

Since I (and you apparently) have no idea what sort of BIND or SEARCH rate your single replica is under, it is hard to know what your requirements are, and I understand you are trying to gather that data. Here, at least, is a comparison, and I have a hard time believing you'd need 20 LDAP replica's in a well designed environment.

Also, the number of replica's to master is an interesting question. It will mostly depend I guess on how many writes you experience in a single day. Again, the information you've provided here is minimal, but unless your master is in a constant state of change, I'd think it'd be able to hold up just fine even with a large number of replicas.


Quanah Gibson-Mount
Principal Software Developer
ITSS/Shared Services
Stanford University
GnuPG Public Key: http://www.stanford.edu/~quanah/pgp.html

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