À La Carte Services HA - Windows Server Failover Clustering
Active-Passive HA for Application Services
Executive Summary
Windows Server Failover Clustering (WSFC) [1] provides an active-passive framework where independent servers (nodes) monitor each other and a shared cluster role, automatically failing over workloads when a node becomes unavailable. This model ensures application continuity but introduces a short interruption during failover. It also relies on deep trust relationships between nodes and Active Directory. While clustering improves availability in the event of hardware and service failures, it also expands the cyberattack surface: the compromise of one node can enable attackers to abuse cluster credentials, impersonate traffic, or poison DNS records, potentially disrupting the entire cluster. Efficiency is one-to-one, requiring a dedicated standby for each protected role.
Failover
Windows Server Failover Clustering[1] (WSFC) provides HA by connecting independent servers (nodes) so that an available node automatically assumes the workloads of a failed one, thereby reducing downtime.
Consistency
WFSC does not provide native data consistency as it is built for service availalbilty and not for data consistency. In the Milestone VMS environment, WSFC is most often applied to stateless services—such as Management, Event, and Mobile. WSFC alone is generally not used for Recorder services, as XProtect includes a native recorder failover mechanism in higher-tier editions, which manages the stateful media database more effectively. See: Media Stack High Availability.
Cybersecurity
WSFC improves availability but introduces a cybersecurity risk because it relies on implicit trust between nodes and shared cluster identities in Active Directory. If an attacker compromises one node, they can harvest its machine credentials and abuse the cluster's accounts to impersonate cluster traffic, forge heartbeats, or poison DNS records. Such manipulation can trigger false failovers, disrupt quorum, or redirect client connections—turning mechanisms built for resilience into vectors for cluster-wide disruption. In effect, WSFC improves availability against hardware failure, but it also increases the blast radius of a cyberattack.
Efficiency
Efficiency is one-to-one, meaning one standby node can support one primary node failure. Two standbys are required to support two simultaneous primary node failures, and so on.
References
Microsoft. Failover Clustering Overview (Windows Server), link
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