Master instances are special instances that run an essential set of services, including:
- Admin-App service
- Cluster-Coordination service
- Synchronization service
- Service-Deployment service
Non-master instances are called workers. Workers can run any services except for those listed previously.
Single-instance systems have one master instance while multi-instance systems have either one or three master instances.
Important: You
cannot add master instances to a system after it's installed. You can, however, add
any number of worker instances.