High Availability (HA) and Clustering both provide redundancy by eliminating the single node as a point of failure. They are able to provide availability in these scenarios:
- 虚拟化主机系统故障，包括 AWS 上未计划和计划内的维护事件。
集群通过跨多个节点分配负载而提供更好的可扩展性。 这种横向扩展能力可能更适合某些拥有数万名开发者的组织。 In HA, the scale of the appliance is dependent exclusively on the primary node and the load is not distributed to the replica server.
|Feature||Failover configuration||Failover method|
|High Availability Configuration||DNS record with a low TTL pointed to the primary appliance, or load balancer.||You must manually promote the replica appliance in both DNS failover and load balancer configurations.|
|Clustering||DNS record must point to a load balancer.||If a node behind the load balancer fails, traffic is automatically sent to the other functioning nodes.|
Neither HA or Clustering should be considered a replacement for regular backups. For more information, see "Configuring backups on your appliance."
Availability features, especially ones with automatic failover such as Clustering, can mask a failure since service is usually not disrupted when something fails. Whether you are using HA or Clustering, monitoring the health of each instance is important so that you are aware when a failure occurs. For more information on monitoring, see "Recommended alert thresholds" and "Monitoring cluster nodes."
- For more information about GitHub Enterprise Server Clustering, see "About clustering."
- For more information about HA, see "Configuring GitHub Enterprise Server for High Availability."