This is a user-to-user forum. If you want an answer from Dell as such, I suggest you call Equallogic support and open a case with them and ask the question. As a non-Dell answer, my wording may not be 100%, but the general idea is that iSCSI uses MPIO. From a host, each NIC/VMkernel generates an iSCSI session to the group. The group then forwards that session to a physical port on the member. So, with 2 NICs/VMkernels on 2 separate IP addresses, that yields 2 iSCSI sessions where each session generally ends up being forwarded to a different physical port on the member. The MPIO part then splits the SCSI commands (inside of TCP traffic) and sends them to the array. This is how you get a 2Gbit/s 'connection'. If you start teaming NICs, the iSCSI connection becomes a single connection, which gets forwarded to a single physical port on the member (which is a 1Gbit/s port (I'm assuming you don't have a 6010 or 6510)), and therefor you just reduced your bandwidth to 1Gbit/s.
There are some people in our department who feel that creating etherchannel bonded port groups on the connections running to our equallogic group are not gaining advantages due to the load balancing algorithms of the equallogic arrays and there are those that are confident that because of the load balancing and multi paths that there is a performance advantage to be gained by running etherchannel.I am interested in what Dell's take is on this. We are strictly talking ESX hosts and vm guests running iscsi initiators.
Etherchannel ESX 4.1 and Equallogic