Slow Read Performance from Storage Arrays - Delayed Ack

I recently stood up an ESX host on 10GbE.   The ESX host is using the Cisco Nexus 1000v connected to a Nexus 5K.  Storage is an Equallogic PS6010, also using 10GbE.

I ran IOMeter tests against this new setup and was disappointed with the poor read performance.  For consistency, the OpenPerformanceTest.icf config file from the following post was used:

http://communities.vmware.com/thread/73745

The IOPs for the Max Throughput -100%Read test was showing 584.   That's considerably slower than our existing production environment using a 1GbE infrastructure.

To resolve this issue, DelayedAck was disabled on the ESX host. TCP Delayed Ack groups together several ACK responses into a single reply. Delayed Ack can be disabled at the Discovery Address level (preferred), OR globally for the vmhba used for iSCSI.

Discovery Address Level - Select the iSCSI server under the Dynamic Discovery tab for your iSCSI vmhba.  Then, uncheck Inherit from Parent, and DelayedAck.  Reboot Host.
Globally - Uncheck DelayedAck in Advanced Setting for the vmhba used for iscsi. Reboot Host.

After making this change, I ran the same test and and was pleasantly surprised by an IOPs score of 22,354!!