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 http://go.microsoft.com/fwlink/?linkid=34707.

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine whether the disk time-out value has been changed from the default value:

HKEY_LOCAL_MACHINESystemCurrentControlSetServicesDiskTimeOutValue

If the Exchange Server Analyzer finds the TimeOutValue present and configured with any value other than 10, and the server is non-clustered, a non-default configuration message is displayed. If the Exchange Server Analyzer finds the TimeOutValue present and configured with any value other than 20, and the server is clustered, a non-default configuration message is displayed.

Disk time-out is a registry setting that defines the time that Microsoft Windows® will wait for a hard disk to respond to a command. On a non-clustered system, this key is not present and a default value of 10 seconds is used for all disks. On a Windows cluster, this key is present and uses a default value of 20 seconds. If the time-out time is more than the value in this registry setting, Windows will show an error and will stop disk access. Sometimes, this may be set to a greater value if you are running multipath disk-access software. Multipath software lets you connect multiple physical paths (such as fiber) to a single disk drive for redundancy. Multipath software manages the multiple physical connections so that Windows handles only a single handle to the disk.

Installing host bus adapters (HBA) or other storage controllers can cause this key to be created and configured. When you install or reinstall these drivers, the TimeOutValue registry value is overwritten with the value that is required by those drivers. You may have to contact the hardware vendor to determine the correct TimeOutValue registry value for your configuration.

To revert to the default configuration