Sun Configuration Information
Application tier scalability is achieved using a highly flexible, horizontally scaled infrastructure. Multiple instances of Blackboard Learn can be deployed on a single Sun server using either a virtualization package or bare-metal configuration to isolate Blackboard application instances from each other and to manage allocation of CPU and memory resources.
Each Sun server in the application tier can run multiple zones each with its own instance of the Blackboard Learn software. To achieve a high volume of concurrent user sessions, the architecture employs load balancing to distribute requests across all of the Blackboard Learn application instances deployed on the zones.
The architecture takes advantage of 64-bit computing by using Java heap sizes that range from 2G to 16GB for each Blackboard application instance. Some customers on rare occasions have deployed Java Virtual Machines (JVMs) as large as 32GB in size. The Java heap had been limited to 1.7GB in a 32-bit environment, but this limitation is overcome in the 64-bit environment. Because this feature is now available for all platforms with Blackboard Learn Release 9.1, Blackboard strongly recommends that customers adopt 64-bit for their primary deployment OSs.
The architecture includes a recommended 8GB of memory for each VM, leaving up to 2GB for the Apache Web server, and up to 2GB for the OS and monitoring tools. This assumes a JVM heap size of 4GB. Obviously, a larger JVM heap size will require additional memory for the VM. The larger memory footprint for Blackboard Learn enables each application instance to more efficiently service a high volume of user requests. In other words, each application instance can scale vertically while the architecture can also be scaled horizontally by deploying additional VMs.
This “best of both worlds” approach takes advantage of many application threads in the application tier to service thousands of requests per minute. The recommended servers for the application tier are Sun SPARC Enterprise T5120 and T5140 models, which were chosen for their small footprint, moderate cost, and powerful throughput performance.
The highly flexible and scalable application tier can help customers achieve:
- Lower costs: Increased utilization of servers enables good performance on a low-cost consolidated infrastructure.
- Increased flexibility: VMs can be moved easily to other physical servers to redistribute workloads or recover quickly from a hardware failure.
- Faster Deployment: With fewer physical systems to setup and configure, less time is required for deployment.
Will Tomcat Clustering Make a Difference?
Tomcat Clustering is deprecated for Blackboard Learn 9.1 Service Pack 6, and will be removed from Blackboard Learn 9.1 Service Pack 8. For alternative solutions, see Optimizing Performance.
Customers should begin migrating from Tomcat clusters. Tomcat clustering was introduced for scalability purposes when the Blackboard Learn architecture was 32-bit and customers wanted the ability to increase their memory usage on a single server. With the option to virtualize on both 32-bit and 64-bit, Blackboard’s benchmarking efforts have moved away from Tomcat cluster deployments. Customers can achieve similar performance in a virtual environment on the same physical server with multiple virtual instances as with a bare metal configuration with many Tomcat cluster instances. The difference in configurations is a smaller demand on the Apache or IIS web server fronting the Tomcat instance(s). The option to deploy a 64-bit JVM with larger heap sizes has suppressed the need for customers to run in a cluster option.
Blackboard recommends that customers consider a deployment approach consisting of larger 64-bit JVMs that are distributed across physical servers with the option to virtualize the hardware to take advantage of the CPU and Memory capacity of these systems.