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

Chapter 23 Understanding Multipathing and FailoverSetting a Path Selection PolicyFor each storage device, the ESXi host sets the path selection policy based on the claim rules.By default, VMware supports the following path selection policies. If you have a third-party PSP installedon your host, its policy also appears on the list.Fixed (VMware)The host uses the designated preferred path, if it has been configured.Otherwise, it selects the first working path discovered at system boot time. Ifyou want the host to use a particular preferred path, specify it manually.Fixed is the default policy for most active-active storage devices.NOTE If the host uses a default preferred path and the path's status turns toDead, a new path is selected as preferred. However, if you explicitlydesignate the preferred path, it will remain preferred even when it becomesinaccessible.Most Recently Used(VMware)Round Robin (VMware)The host selects the path that it used most recently. When the path becomesunavailable, the host selects an alternative path. The host does not revertback to the original path when that path becomes available again. There is nopreferred path setting with the MRU policy. MRU is the default policy formost active-passive storage devices.The host uses an automatic path selection algorithm rotating through allactive paths when connecting to active-passive arrays, or through allavailable paths when connecting to active-active arrays. RR is the default fora number of arrays and can be used with both active-active and activepassivearrays to implement load balancing across paths for different LUNs.Change the Path Selection Policy in the vSphere Web ClientGenerally, you do not have to change the default multipathing settings your host uses for a specific storagedevice. However, if you want to make any changes, you can use the Manage Paths dialog box to modify apath selection policy and specify the preferred path for the Fixed policy.Procedure1 Browse to the host in the vSphere Web Client navigator.2 Click the Manage tab, and click Storage.3 Click Storage Devices.4 Select the storage device whose paths you want to change and click the Properties tab.5 Under Multipathing Properties, click Edit.6 Select a path selection policy.By default, VMware supports the following path selection policies. If you have a third-party PSPinstalled on your host, its policy also appears on the list.• Fixed (VMware)• Most Recently Used (VMware)• Round Robin (VMware)7 For the fixed policy, specify the preferred path.8 Click OK to save your settings and exit the dialog box.VMware, Inc. 225