Performance improvement with DNS cache
We suggest to add in the documentation a tip that have improved substantially the performance and reliability of our system.
On linux, by default, there is no DNS cache and portals request DNS at every connexions on LDAP and DB... Under heavy loads, we had hundred of DNS queries and many many errors on LDAP connexions (timed out) from IO::Socket. The DNS server was saturated with CPU and IO !
After installing nscd and activated the hosts cache on all servers, and especially on portals, the DNS load fell quickly and timeouts errors disappeared.
nscd works well for us and is easy to setup on debian and rhel, but other solutions exists (netmasq, bind...). There is a problem on TTL with nscd but it's not a problem for us.