(Particularly on 1Gps links)
Ensure at least 2 paths to each device, and set each path to Round Robin.
Set disk max IO to 512 from 32k
https://kb.vmware.com/kb/1003469
Set Round Robin max IOPS to 1 from 1000:
https://kb.vmware.com/kb/2069356
The max IOPS made the biggest difference in my lab. With default IOPS set to 1000:
With IOPS set to 1:
