(Failover Cluster) failover cluster가 어떻게 failure를 인지하는지

In a failover cluster, the failover mechanism is the process by which workloads are automatically shifted from a failing node to a healthy node in the cluster. This ensures minimal disruption to services and maintains high availability. The mechanism involves monitoring the health of each node and, upon detecting a failure, transferring the workload to another node. 

 

Here's a more detailed explanation:

 

 

1. Monitoring and Detection:

• Heartbeat:

  Each node in the cluster periodically sends a heartbeat signal to other nodes, indicating its health status. 

   
• Monitoring Software:

  The cluster management software continuously monitors the status of each node and the resources it manages. 

   
• Failure Detection:

  If a node fails to respond or its health status becomes critical, the monitoring software detects the failure. 

   

2. Failover Process:

• Automatic Transfer:

  When a failure is detected, the cluster management software automatically transfers the workload (applications, services, data) from the failed node to a healthy node. 

   
• Resource Relocation:

  This may involve relocating virtual machines, databases, file shares, and other resources to the new node. 

   
• Network and Storage:

  Network and storage resources are also managed to ensure seamless continuity of service. 

   

3. Key Considerations:

• Quorum:

  A quorum is a mechanism that ensures the cluster can make authoritative decisions, even in the event of node failures. It helps prevent split-brain scenarios where multiple nodes believe they are the primary. 

   
• Shared Storage:

  Failover clusters typically rely on shared storage, allowing multiple nodes to access the same data. 

   
• Data Replication:

  Data replication ensures that the latest data is available on the standby node, enabling seamless failover. 

 

 

https://learn.microsoft.com/en-us/sql/sql-server/failover-clusters/windows/windows-server-failover-clustering-wsfc-with-sql-server?view=sql-server-ver16