What is a reason for assigning FSMO roles to some DCs?

Assigning Flexible Single Master Operations (FSMO) roles to certain Domain Controllers (DCs) is essential because it designates specific DCs as the only ones authorized to perform particular critical functions within the Active Directory environment. These roles include tasks such as schema updates, domain naming, and managing relative IDs. By centralizing these tasks, it prevents conflicts that could arise from multiple DCs trying to execute the same function simultaneously, ensuring smooth and consistent operations within the directory services.

While redundancy is important, and all DCs should have the capability to support each other in various ways, the specific assignment of FSMO roles is inherently about avoiding duplication of these critical tasks, not about having multiple DCs handling the same roles simultaneously. Likewise, the identical role performance across all DCs is not feasible due to the specialized nature of FSMO responsibilities. Load balancing is also not a primary purpose for FSMO roles; rather, it's about delegation of specific, necessary functions to streamline directory operations effectively.