Samba can store user and machine account data in a “TDB” (trivial database). Using this backend does not require any additional configuration. This backend is recommended for new installations that do not require LDAP.

As a general guide, the Samba Team does not recommend using the tdbsam backend for sites that have 250 or more users. Additionally, tdbsam is not capable of scaling for use in sites that require PDB/BDC implementations that require replication of the account database. Clearly, for reason of scalability, the use of ldapsam should be encouraged.

The recommendation of a 250-user limit is purely based on the notion that this would generally involve a site that has routed networks, possibly spread across more than one physical location. The Samba Team has not at this time established the performance-based scalability limits of the tdbsam architecture.

There are sites that have thousands of users and yet require only one server. One site recently reported having 4,500 user accounts on one UNIX system and reported excellent performance with the tdbsam passdb backend. The limitation of where the tdbsam passdb backend can be used is not one pertaining to a limitation in the TDB storage system, it is based only on the need for a reliable distribution mechanism for the SambaSAMAccount backend.