In terms of the SPOFs that are described at the beginning of this chapter, redundancy handles failure in the following ways:
Single hardware failure. A single hardware failure is fatal to a machine. Therefore, even if you have redundant hardware, manual intervention is required to repair the failure.
Directory Server or Directory Proxy Server failure. The server is automatically restarted.
Database corruption. Depending on the architecture, a redundant solution should be able to survive database corruption.