When expanding a PowerFlex rack solution, optimizing the redundancy of the MDM roles is crucial to maintain system resilience and availability. The best practice in such a scenario is to distribute the MDM roles across the available cabinets to prevent a single point of failure. This can be achieved by adding Standby MDMs to the newly added cabinets1.

Here’s a step-by-step explanation:

Assess the current MDM configuration: Understand the current setup of MDMs and Tie-breakers in the existing cabinets.

Plan for distribution: Decide on how to distribute the MDM roles across the expanded infrastructure to enhance redundancy.

Add Standby MDMs: Introduce Standby MDMs in the new cabinets (Cabinet 3, Cabinet 4, and Cabinet 5) to ensure that each cabinet has an MDM role, enhancing the fault tolerance of the system.

Configure Standby MDMs: Properly configure the Standby MDMs to take over in case the Primary or Secondary MDMs fail.

Test the configuration: After adding the Standby MDMs, test the system to ensure that the MDM roles can failover smoothly without impacting the system’s performance or availability.

By adding Standby MDMs to the new cabinets, you ensure that the MDM roles are not concentrated in a single cabinet, which could lead to a higher risk of system downtime if that particular cabinet encounters issues. This approach aligns with the best practices for designing resilient and high-availability systems1.

The other options do not provide the same level of redundancy optimization. For instance, moving MDM 3, Tie-breaker 1, and Tie-breaker 2 to separate cabinets (Option A) does not address the need for additional Standby MDMs in the new cabinets. Changing the MDM Cluster Mode from three-node to five-node (Option C) is not necessary for redundancy and may introduce unnecessary complexity. Consolidating MDM 2 and Tie-breaker 1 into Cabinet 1 (Option D) would reduce redundancy rather than optimize it.

Therefore, the correct answer is B. Add Standby MDMs to Cabinet 3, Cabinet 4, and Cabinet 5, as it provides a distributed and resilient MDM configuration suitable for an expanded PowerFlex rack solution.