In Azure Stack HCI and Windows Server 2019, there are two components of the system that have their own quorum mechanisms: Once nodes which have been stopped can once again communicate with the main group of nodes, they will automatically rejoin the cluster and start their cluster service. By having this concept of quorum, the cluster will force the cluster service to stop in one of the subsets of nodes to ensure that there is only one true owner of a particular resource group. Quorum is designed to handle the scenario when there is a problem with communication between subsets of cluster nodes, so that multiple servers don't try to simultaneously host a resource group and write to the same disk at the same time. Quorum determines the number of failures that the cluster can sustain while still remaining online. However, this is prevented with Failover Clustering's concept of quorum which forces only one of these groups of nodes to continue running, so only one of these groups will stay online. This can cause both subsets of nodes to try to own the workload and write to the same disk which can lead to numerous problems. Quorum is designed to prevent split-brain scenarios which can happen when there is a partition in the network and subsets of nodes cannot communicate with each other.
These resources are considered highly available if the nodes that host resources are up however, the cluster generally requires more than half the nodes to be running, which is known as having quorum.
Windows Server Failover Clustering provides high availability for workloads running on Azure Stack HCI and Windows Server clusters. Applies to: Azure Stack HCI, versions 22H2 and 21H2 Windows Server 2022, Windows Server
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