Host Bus Adapter queue depth is set to 32

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at]  

Topic Last Modified: 2006-10-11

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine the queue depth of the host bus adapters (HBAs) installed in the Exchange Server computer:


If the Exchange Server Analyzer finds the value for DriverParameter to be set to 32, a warning is displayed.

An HBA is a disk controller for storage area networks (SANs). The HBA queue depth defines the maximum number of outstanding queue requests. Generally, the recommended value for DriverParameter is 128. However, this may not be the optimal value for the HBA queue depth for every HBA in every Exchange Server computer. Therefore, you should consult with the HBA manufacturer to obtain the optimal value for your specific hardware.

To correct this warning

  1. Contact your hardware manufacturer to determine the optimal setting for your HBAs.

  2. Monitor disk performance using the Microsoft Windows® System Monitor utility.

  3. Update your HBA hardware to the latest firmware and drivers.

For more information about Exchange Server storage design and optimization, see the "Optimizing Storage for Exchange Server 2003" (