This may be because there has not been enough traffic to cause a path switch:
From: VMware KB: Multipathing policies in ESXi 5.x and ESXi/ESX 4.x
- The Round Robin (RR) multipathing policies have configurable options that can be modified on the command line. Some of these options include:
- Number of bytes to send along one path for this device before the PSP switches to the next path.
- Number of I/O operations to send along one path for this device before the PSP switches to the next path.
esxcli storage nmp psp roundrobinin the vSphere Command-Line Interface Installation and Reference Guide for the appropriate version of your VMware product.- If the storage device is configured for Asymmetric Logical Unit Access (ALUA), Round Robin by default will use only the active optimized paths. Note: This behavior can be changed, but not recommended as it may result in performance degradation. For more information, see Managing NMP with esxcli storage nmp section of the vSphere 5 Documentation.
- To change a LUN to use the Round Robin path policy, see Changing a LUN to use a different Path Selection Policy (PSP) (1036189).
- To change newly provisioned LUNs to use Round Robin by default, see Changing the default pathing policy for new/existing LUNs (1017760).
- For more information, search for Multipathing Considerations and PSP in the vSphere 5 Documentation Center ; for 5.5 vSphere 5.5 Documentation Center
- For translated versions of this article, see: