The reliability of such a telecom box also hinges on the controller card, that's a critical component and certainly a potential SPOF (single point of failure). You can increase the reliability of this telecom box by using additional controller cards.
The additional controller card is for redundancy. Add another controller card as shown below:
Once the (second) controller card is installed, the challenge is in the determination of the primary controller card. This is done by the software running on the controller cards. By default, applications on the data cards access the primary controller card. Assuming cc0 is the primary controller card, Use the following command to access this card in /cc directory:
ln -s /net/cc0 /cc
The above indirection makes communication between data card and controller card transparent. In fact, the data cards remain unaware of the number of controller cards, or which card is the primary controller card.
Applications on the data cards access the primary controller card. In the event of failure of the primary controller card, the secondary controller card takes over. The applications on the data cards redirect their communications via Qnet to the secondary controller card.