| Replication has always been the "Crown Jewel" of the Lotus Notes and Domino product. Domino cluster replication technology allows a group of Domino servers to work together to appear to the user as if they were a single Domino server. The cluster is used to provide high availability of data and services, to balance workload, and to significantly increase the number of users your system can support (scalability). Servers in a Domino cluster use cluster replication (real-time replication) to keep all servers in the cluster the same. If one server in a cluster goes down, users are transparently switched to another server in the cluster (failover). Cluster workload balancing ensures that heavily used servers are able to pass requests to other cluster servers and that work is evenly distributed across the cluster. Additional servers can easily be added to a cluster to allow the Domino service, with workload balancing, to scale to a very large number of users. Domino 6 Streaming Replication Streaming replication involves a single server request, which then pulls in all the data (Notes documents and their attachments) into the database. This feature dramatically reduces replication time and works in all Domino 6 client/server scenarios. Streaming replication also means that when using the Notes client, you no longer have to wait until the replication is over before seeing replicated documents in folders. They appear individually as soon as they are pulled into the system, and you can begin to work on them before the database has finished replicating. In addition, documents are replicated in ascending order by size . To use streaming replication, both parties involved in the replication must be running Notes/Domino 6. Streaming replication is PULL only. This feature uses a single streamed RPC (Remote Procedure Call) to read a number of documents and attachments. This is an improvement over the non-streaming method of requesting and acknowledging one database note at a time. Streaming replication saves time and consumes less CPU and network activity to replicate the same number of documents. Network latency is reduced, especially on slower links. Documents are also replicated in ascending size order (smallest first). This allows the client to abort a long replication but still receive some documents (for example, mail). Partial replication is also supported, allowing an aborted replication to be reinitiated and to continue where it left off. Views in folders are also updated incrementally while a replication is in progress (as opposed to the end of replication). This allows users to begin responding to initial documents (mail messages, for example,) while larger documents continue downloading. End-user benefits of streaming replication include shorter replication times, ability to start viewing and working on documents before replication is completed, and replication of smallest documents first. If replication is cancelled, the target system still has documents (especially smaller ones) that were replicated before the replication session ended. Incrementally updated folders means you no longer have to wait until the replication is over before seeing replicated documents in folders. Advantages for IT departments (for example, server to server replication) include faster replication, partial replication, potentially less network traffic due to single streamed RPC, and reduction of ACK (Acknowledgment) TCP/IP responses. Lotus found that databases with 10,000 and 25,000 documents replicated 15% faster with streaming replication on. A database with 50,000 documents replicated 60% faster with streaming replication on. Domino 6 Network Compression Network compression is an important performance feature offered in Notes/Domino 6. When you enable network compression, data is automatically compressed before it is sent over the network. This improves network performance, especially over slower line speeds. With network compression enabled on both the sending and the receiving computers, the Notes client and/or the Domino server attempts to compress any data (for example, mail or replicated documents) before transmitting it over the network. Network compression works with mail routing, replication, or any other data sent via NRPC (Notes Remote Procedure Call). This includes design elements in new or updated replica databases. Notes/Domino 6 network compression offers a number of immediate benefits. For example, by reducing the amount of data being transmitted, you can improve the performance of your routing and replicating hub servers, especially if they are currently laboring under heavy workloads. You also can enable it by default so that all your users with Notes 6 clients can take advantage of this functionality without having to select it themselves . Because network compression is a standard, out-of-the-box feature, it doesn't require any additional code, which helps simplify administration. CPU and memory resources used on the system increase by a small amount. In many of the environments where it is very expensive or not even even an option to upgrade the existing network infrastructure, this is a welcome trade-off. Lotus also enhanced attachment compression in Domino 6. Attachment compression can now take advantage of the LZ1 (Lempel-Ziv) algorithm (the same algorithm used in network compression). In R5, attachment compression used the Huffman algorithm. To use LZ1 compression in Domino 6, you must enable it in the Database Properties box. (By default, databases still use the Huffman algorithm to maintain backward compatibility.) The LZ1 attachment compression typically reduces attachment file size by 5% to 40% over Huffman attachment compression. The percent reduction in size depends upon the type and complexity of the file attachment. HTTP Server Plug-In Both WebSphere and Domino have HTTP server capability. Starting from WAS 4.0, the HTTP server is also embedded in WAS itself. The HTTP handling capability embedded within the application server supports a connection from an HTTP client to the Application Server. An HTTP client can connect to a Web server, and the HTTP plug-in can forward the request to the Application Server. | 