Vertical and Horizontal Scalability, Load Balancing, and Performance Factors
Depending on the requirements and scale of the implementation, the application server tier can be scaled both vertically (adding resource to the application server) and/or horizontally (adding additional application servers in parallel), and the database server can be scaled both vertically (adding resources to the database server) and/or horizontally (clustering database servers via the database vendor’s native functionality).
When multiple application servers are deployed in a single instance, a load balancer is typically configured between the end user workstation and the application servers.
Network and Storage Recommendations (WAN Latency, Storage I/O Latency, RAID)
For general end users, network latency to the application should be < 30 ms and bandwidth > 1 Mbps. For lightweight users, latency should be < 100 ms and bandwidth > 256 Kbps.
For higher latency or lower bandwidth, special considerations in functional design can be applied, as can WAN accelerators or Citrix-based deployments.
For database-intensive deployments, dedicated storage for the database is recommended. RAID‑1+0 is preferred with latency < 10ms for performance at the database tier, or minimally for temp/redo/log table spaces.