In a non-clustered system, all Unwired Platform server components (the Unwired Server and data tier servers) are installed by a single installation procedure, on a single host.
It cannot be scaled by adding or subtracting servers, to adapt to changes in system load or performance requirements.
It cannot take advantage of conventional load-balancing and failover mechanisms to provide higher system availability.
The only sure way to increase overall system performance is to upgrade the host system resources (CPU, RAM, etc.).
When you choose between clustered and non-clustered designs, you must plan carefully. If you can reasonably foresee any future requirement for a clustered system, such as a service level agreement (SLA) that would require scalability, or higher system availability), you should consider deploying a clustered Unwired Platform system.