An Unwired Server cluster provides highly available services to remote-device clients, typically requiring one or more relay servers and an optional load balancer.
When you install Sybase Unwired Platform, a cluster is created automatically, and Unwired Server is added to it.
By default, the cluster name is the name of the first host on which you install Unwired Server. Each server can be a member of only one cluster. Cluster configuration properties are saved in the cluster database, which is managed by the data tier.
For high availability, at least two servers must be defined for a cluster. However, to create a load-balanced system, many clients then also use a relay server. Without a relay server, clients require custom logic to determine which Unwired Server will directly receive requests. However, a relay-server free environment is not a highly available environment, nor can requests be distributed equally across multiple servers. Consequently, Sybase recommends that you always use a relay server.