Q: Users backend for Proftpd /Apache - Mysql or LDAP? We have two separate sites, each having one host with ProFTPd and Apache authenticating users against /etc/passwd.This requires managing two separate password files and we would like to have  a replicated backend.    
I can see at least two options - MySQL database and LDAP directory.Both can be replicated and used as authentication backend for either ProFTPd or Apache.  
What are the pros and cons of  each solution? 

A: Both MySQL and LDAP work well, pick the one you are already familiar with. :)
If you already have MySQL in use, the one clear advantage of choosing MySQL would be that you could use your existing infra-structure without any new components.
OpenLDAP can be a bit painful to set up, but under extreme load it probably is faster for authentication than MySQL. For frequent writes OpenLDAP is not optimal choice, since LDAP in general has been designed for read-oriented workloads.
