vsphere-esxi-vcenter-server-55-storage-guide

Chapter 23 Understanding Multipathing and FailoverFigure 23‐4. Port Reassignment10.0.0.110.0.0.2storage10.0.0.110.0.0.110.0.0.2storageWith this form of array-based failover, you can have multiple paths to the storage only if you use multipleports on the ESXi host. These paths are active-active. For additional information, see “iSCSI SessionManagement,” on page 97.Path Failover and Virtual MachinesPath failover occurs when the active path to a LUN is changed from one path to another, usually because ofa SAN component failure along the current path.When a path fails, storage I/O might pause for 30 to 60 seconds until your host determines that the link isunavailable and completes failover. If you attempt to display the host, its storage devices, or its adapters, theoperation might appear to stall. Virtual machines with their disks installed on the SAN can appearunresponsive. After failover is complete, I/O resumes normally and the virtual machines continue to run.However, when failovers take a long time to complete, a Windows virtual machine might interrupt the I/Oand eventually fail. To avoid the failure, set the disk timeout value for the Windows virtual machine to atleast 60 seconds.Set Timeout on Windows Guest OSIncrease the standard disk timeout value on a Windows guest operating system to avoid disruptions duringa path failover.This procedure explains how to change the timeout value by using the Windows registry.PrerequisitesBack up the Windows registry.Procedure1 Select Start > Run.2 Type regedit.exe, and click OK.3 In the left-panel hierarchy view, double-click HKEY_LOCAL_MACHINE > System >CurrentControlSet > Services > Disk.4 Double-click TimeOutValue.5 Set the value data to 0x3c (hexadecimal) or 60 (decimal) and click OK.After you make this change, Windows waits at least 60 seconds for delayed disk operations to completebefore it generates errors.VMware, Inc. 219