Deploying for Scalability

Scaling out involves adding multiple BizTalk servers until the SQL Server Message Box database becomes the bottleneck because of severe contention. Thereafter, it is recommended to scale out the database tier, adding Message Box databases. This will help support more BizTalk servers. When the SQL tier again becomes the bottleneck, adding more Message Box databases will help scale out adding more BizTalk servers. However, this design does not scale ad infinitum. Ultimately, the Master Message Box will get saturated supporting, or routing data to, multiple Message Box databases. When this happens, it is recommended to scale up the Master Message Box database, adding more CPUs and/or faster disks.

Scaling Out BizTalk Servers

BizTalk Server 2004 is a persistent messaging system whereby all data is persisted to disk. However, no data is persisted locally on the BizTalk servers; all data is persisted within multiple SQL Server database tables. All orchestration and adapter code, with the exception of the HTTP and SOAP receive adapters, is hosted within the BizTalk Server service. The HTTP and SOAP adapters are hosted within an ISAPI extension (BTSHTTPReceive.dll) shipped with the product. After the product is installed and configured, either by creating or joining the BizTalk Group on the BizTalk servers to reference the SQL Server databases, what needs to be done next is to logically group machines using hosts. Further, it is necessary to add the compiled scenario/assembly to the GAC locally on all the BizTalk server machines. In addition to deploying the assemblies, any resources, such as SOAP Web services, HTTP Vroots, File Receive locations, and so on required to support the scenarios must be set up. The Scenario (assemblies) also needs to be deployed—that is, artifacts added into the BizTalkMgmtDb database—from at least one of the BizTalk servers. Although BizTalk can be configured to run on a single machine, when scaling out it is recommended to first separate the SQL databases onto a dedicated server, preferably with high-speed disks.