E-Series Controller Firmware 8.xx
By default, VMware ESXi (5.x/6.x) utilizes the Round Robin (RR) Path Selection Policy (PSP) for volumes mapped from storage arrays with the 'NETAPP' Vendor ID/Product ID. This policy attempts to balance the I/O load across all active storage paths, based on the number of I/Os or bytes transmitted. By default, RR will attempt this re-balancing after every 1000 I/Os, or 10485760 bytes.
Although not required, adjusting the I/O counter might improve performance in instances where an active storage path might have several queued I/Os. For instance, with the default I/O counter of 1000, any I/O in a storage path's queue must wait until that storage path can service the request. Modifying this limitation to 1 allows other active storage paths to service new I/O requests.
For more information, see VMware KB 2069356.