Not all the Excel Calculation Service servers may be used when you use Excel Web Access to load workbooks and when URL load balancing is enabled

Consider the following scenario:

• You have a Web front-end server that contains Microsoft Office SharePoint Server 2007 Excel Services Web components.
• You have three application servers that are running the Excel Calculation Service (ECS).
• You have computers that are set up in a farm environment and that are set to use Workbook URL load balancing.
  
  Note By default, Excel Services uses the Workbook URL load balancing scheme.

In this scenario, not all the ECS servers may be used when you use Excel Web Access to load three distinct workbooks.

Note You expect that each ECS server could receive one workbook.

This behavior occurs when you use the Workbook URL scheme because a hash of the workbook URL determines which ECS server receives the request. This logic could direct all requests to a single ECS server, distribute the requests evenly among all available ECS servers, or distribute the requests to several but not all ECS servers.

This behavior is by design.

In an Excel Calculation Services server farm, workbooks are distributed evenly among the servers. The more workbooks that are open in the environment the more evenly the workbooks will be distributed among the servers.

For more information about Excel Services, visit the following Microsoft Developer Network (MSDN) Web site: