A question that I get asked frequently revolves around iscsi multipathing options and how folks would be provide redundancy and be able to route I/O around various failed components residing in the data path.
Contrary to what has been available for Fibre Channel, iSCSI offers multiple choices to select from, each of which has various characteristics. So here are your optionsm most of which are available across all Operating systems that provide iSCSI support today:
1) Link Aggregation - IEEE 802.3ad
Link Aggegation, also known as Teaming or Trunking, is a well known and understood standard networking technique deployed to provide reduncancy and high-availability access for NFS, CIFS as well as other types of traffic. The premise is the ability to logically link multiple physical interfaces into a single interface thus providing redundancy, and higher availablity. Link aggregation is not dependent on storage but rather a capable Gigabit Ethernet driver.