Increase the standard disk timeout value so that a Windows guest operating system is not extensively disrupted during a path failover.

Path failover occurs when the active path to a LUN is changed from one path to another, usually because of some SAN component failure along the current path.

I/O might pause for 30 to 60 seconds until the iSCSI driver determines that the link is unavailable and until failover is complete. As a result, the virtual machines (with their virtual disks installed on SAN storage) can appear unresponsive. If you attempt to display the host, its storage devices, or its adapter, the operation might appear to stall. After failover is complete, I/O resumes normally.

In case of multiple breakages, all connections to SAN storage devices might be lost. If none of the connections to the storage device is working, some virtual machines might encounter I/O errors on their virtual SCSI disks.

For Windows 2000 and Windows Server 2003 guest operating systems, you can set operating system timeout by fusing the registry.


Back up your Windows registry.


Select Start > Run.


From the command prompt type regedit.exe, and click OK.


In the left-panel hierarchy view, double-click HKEY_LOCAL_MACHINE, then System, then CurrentControlSet, then Services, and then Disk.


Select the TimeOutValue and set the data value to x03c (hexadecimal) or 60 (decimal).

After you make this change, Windows waits at least 60 seconds for delayed disk operations to complete before it generates errors.


Click OK to exit the Registry Editor.