We have a MD3000i connected to a iSCSI San for VM Ware, 4 ESX servers and 2 VC servers, connected to a 6905 cisco switch.  Two controllers in the MD3000i and 2 NICs in each of the ESX servers and VC servers dedicated to iscsi.  All of these are on one subnet for the iscsi.  We are getting great reads but poor rights.  About 1.4mb for rights and 3-4 for reads.  A few questions

What is acceptable throughput for this iSCSI.  What can be tweeked? 

Thanks