BizTalk 2006 Whitepaper on Clustered Solutions
Check out Improving Fault Tolerance in BizTalk Server 2006 by Using a Windows Server Cluster. While the BizTalk engine does messaging/processing load balancing itself among the various hosts, there are definitely parts of a BizTalk architecture that must be explicitly clustered if you're serious about availability. For instance, the underlying SQL databases, Single Sign On, certain adapter end points (e.g. MSMQ, File) and more.
On a quasi-related note, I like the new Dev Center, but apparently I have to put a horse head in someone's bed to actually get this blogs listed on the BizTalk blogs page. Don't think I won't do it.
Technorati Tags: BizTalk