OpenLDAP Scaling

HI,

I'm trying to scale out a openldap server deployment to serve around 100K users. I plan on having a master server and using syncrepl to create slaves that sit behind a load-balancer. Is there a good rule of thumb to abide by when creating a scenario like this? How many authentications/sec can a server typically handle? I've seen the benchmark comparisons ( http://www.usenix.org/event/lisa07/htgr_files/chu.pdf) that have been posted by Howard, but it doesn't say what the system specs were that the tests were performed on? I will have pretty beefy systems to use (lots of RAM and CPU)...

Thanks!!