About protecting against robotic control connection failures
In tape-based backup environments, the robotic control connections can be single points of failure. The inability to send instructions to the tape library prevents backup and restore operations, even if the tape drives are available.
Some tape libraries, such as Sun STK ACSLS or Quantum ATM, use a dedicated control software that runs on a server that is independent of the library. Such control servers can be clustered. The media servers send requests to the control server, which handles the movement of tapes between slots and drives in the library.
Other tape libraries depend on a direct device connection from the NetBackup master server for control instructions to the library. If this device connection is lost, the tape library cannot be used. SAN-attached tape libraries support multiple connections to the robotic control for redundancy. You can configure these connections to provide protection against server failure. For example, you can configure one path to each node of a clustered master server. You must ensure that the paths are not active at the same time. If both paths are active, conflicting instructions can be issued, which could result in backup failure or data loss.