Scalability is critical to organizations needing to make the most cost-effective use of their computing resources, handle peak workloads, and grow their infrastructure as rapidly as their business grows. Keep these points in mind:
How the system responds to increasing workloads: what performance it provides, and as the workload increases, whether it crashes or enables performance to gracefully degrade.
How easy it is to add processors, CPUs, storage, and I/O resources to a system or network to serve increasing demands from users.
Whether the same environment can support applications as they grow from low-end systems to mid-range servers and mainframe-class systems.
When deployed in a two-tiered architecture, the Communications Suite offering is meant to scale very effectively in a horizontal manner. Each functional element can support increased load by adding additional machines to a given tier.
In practice, the method for scaling the front-end and back-end services differs slightly.
For Tier 1 elements, you start the scaling process when traffic to the front end grows beyond current capacity. You add relatively low cost machines to the tier and load balance across these machines. Thus, load balancers can precede each of the Tier 1 service functions as overall system load, service distribution, and scalability requirements dictate.
For Tier 2 elements, you start the scaling process when the back-end services have exceeded user or data capacity. As a general rule, design the Tier 2 services to accommodate just under double the load capacity of the Tier 1 services.