When using a Zadara VPSA with VMWare over iSCSI or FC latency may be experienced on the VMWare side when there are no signs of latency on the VPSA. This can be due to the VMWare Round Robin IOPS limit setting. By default the value for this setting is set to 1000. Reducing the VMWare Round Robin IOPS limit from 1000 to 1 can resolve the high latency on the VMWare side.
See VMWare knowledge base article below for additional details