Hello, @fzyzcjy
To answer your question, yes. Mattermost supports high availability clustering for E20 license offering based on the High Availability Cluster (E20).
No specific number / information from the official documentation. However, upon failure of one component, the remaining application servers, database servers, and load balancers must be sized and configured to carry the full load of the system. If this requirement is not met, an outage of one component can result in an overload of the remaining components, causing a complete system outage.