Exchange 2003 clustering and Windows 2003 SP1
Right now, I only have two major customers, though I help CTA Engineering, Dell Professional Services, and Microsoft Consulting Services out with others. Clustering is something I generally try to avoid, but the customer is always right. So, I end up working around clusters.
I am helping prepare one of my customers for updating to Windows 2003 SP1 (my other major customer is already working on getting their 300+ servers upgraded. The customer I'm currently helping with their upgrade plans have all of their 20,000 mailboxes on clustered nodes and make heavy use of Outlook Web Access. So, a little incompatibility I stumbled across in the Windows Server 2003 Service Pack 1 Application Compatibility article is really valuable for these folks.
It points to an KB Article 841561 which describes a situation where OWA clients may receive the 500 - Internal Server Error if an end-user tries to access their mailbox. Yuck! Anywho, there is a fix for this (that updates the the server's DAVEX.DLL component. This is documented and the fix can be downloaded in Update for Exchange 2003 (KB 841561).