Performance and Operations Guides in TechNet

Microsoft BizTalk Server Performance Optimization Guide
http://technet.microsoft.com/en-us/library/cc558617.aspx

Microsoft BizTalk Server Operations Guide
http://technet.microsoft.com/en-us/library/cc296643.aspx

BizTalk Server Database Optimization
http://technet.microsoft.com/en-us/library/bb743398.aspx