Failure in Directory Server or Directory Proxy Server can include the following:
Excessive response time
Write overload
Maximized file descriptors
Maximized file system
Poor storage configuration
Too many indexes
Read overload
Cache issues
CPU constraints
Replication issues
Synchronicity
Replication propagation delay
Replication flow
Replication overload
Large wildcard searches
These SPOFs can be mitigated by having redundant instances of Directory Server and Directory Proxy Server. Redundancy at the software level involves the use of replication. Replication ensures that the redundant servers remain synchronized, and that requests can be rerouted with no downtime. For more information, see Using Replication and Redundancy for High Availability.