iIS Process Engine Components
Chapter 1 Introduction: iIS Process Management 35
Full Configuration: Failover and Load Balancing Combined
To deal with heavy loads on the engine and overcome the potential bottleneck of a
single database service, additional database services can be added to the failover
engine configuration, as illustrated in Figure 1-4.
With a heavily loaded engine, large numbers of state changes need to be written to
the engine database simultaneously. Database access is likely to be a performance
problem. To accommodate large loads, database access is shared among a set of
database service components (which may be running on different nodes) using a
database service router in the primary engine unit.
Each service is assigned a unique name and allocated a priority (depending,
perhaps, on its host node—see “Engine Component Partitioning” on page 85).
When the engine unit needs to access the database, the router provides it the
highest priority database access service available. If there are a number of services
of equal priority available, the router chooses a database service on a round-robin
basis, thus sharing the load among all available services.
Figure 1-4 Engine Configuration with Both Failover and Load Balancing
iIS Process
Engine
Backup
Engine
Unit
Governor
Primary
Engine
Unit
Router
Engine
Database
Database
Services
Database
Services
Database
Services
Client Applications