Marcelo wrote:

Hi,

My organization works with public software, and we are interested in use OpenLDAP to control close of 100,000,000 users. Is it a good idea? What kind of database can we use? Is there some research that points what is the limit for the volume of users?

Whether or not it is a good idea mostly depends on what you need to do with the data, and what software will be used to access it. If most of your apps already support LDAP then it's probably a good idea.

There are no capacity limits in OpenLDAP. We have tested back-bdb and back-hdb with over 5 billion users. No other directory server in the world has scaled to sizes like this while delivering useful performance.

The only limits are your own - your patience, and the performance of the machines you use to house the database. There are no secret tricks - good performance requires sufficient RAM and fast bandwidth to memory, disks, and network interfaces. Raw CPU performance is much less important here than aggregate bandwidth.