High availability
A Webserver cluster keeps the control plane available when a server fails. Several Webservers hold the same data; one of them is active and the others stand by, ready to take over within seconds, with nothing lost.
High availability is optional. Without an HA block in webserver.json the Webserver is standalone and nothing in this section applies.
| Property | Value |
|---|---|
| Model | One active Webserver at a time, automatic failover |
| Nodes | 3 votes: 2 Webservers + 1 witness, or 3 Webservers |
| Failover | Typically 4 to 6 seconds; about 1 second for a planned stop |
| Data | Every change is copied to a majority of the nodes before it takes effect |
| Extra software | None: no external database, no shared disk, no cluster manager |
| License | One cluster license listing every Webserver of the cluster |
Where to start
| You want to | Read |
|---|---|
| Build a cluster now, step by step | Quick start: Webserver cluster |
| Understand what a cluster does and needs | How it works |
| Look up a setting, the front door, the shared address, the Webserver-Front | Configuration |
| Know what the license allows, and what happens with one server left | License |
| Maintain, replace a node, recover a cluster, go back to standalone | Operations |
| Fix a problem | Troubleshooting |