I recently worked at a client site and found it difficult to explain the various configuations for iSCSI so i have detialed them here:
Dedicated hardware for the Storage and Server connected devices keeping normal Network traffic separate from Storage network traffic due to their differing characteristics.
Segmentation – iSCSI should reside in its own vlan, and shutdown vlan1
Spanning Tree Protocol: RSTP/MST has superior port states and topology exchange mechanisms, compared to classic STP (802.1D).
Jumbo Frames– enable MTU 9216 on the switch and MTU 9000 on ESXi.
Flow Control – to be enabled on all ports, end to end, using ‘flowcontrol mode desire’ allowing the far end negotiation.
Storm Control – disabled for unicast, enabled for Multicast/Broadcast
Trunks – by default the switch will transport all vlans across the link. Only add vlans that are required. Because Cisco maintains per vlan instances of STP. More vlans means more complexity and heavier processing on the switch.
Dot1q – Explicitly set to dot1q and nonegotiate. Prevents against waste of generating/processing for Dynamic Trunking Protocol frames over the link.
Latest firmware is a given.