ESX 4 iSCSI Multipathing

There I was, setting up a small DR site for a client, hardware was a blinged up Proliant DL380, connecting to a sweet, sweet little EMC AX4-5i SAN. This being my first non-FC SAN, I obviously investigated the multipathing options. I was kind of (no, really!) taken aback when I discovered that it's not so straightforward to set up. What's a boy to do? I took a deep breath, bowed in the direction of the (not-so-sweet-anymore) AX4-5i SAN and unleashed the fury of my Google-Fu! Hee-Ya! About 3 hours later the fiendish ESX 4 and a AX4-5i had to yield to the fury of my touch typing - below I chronicle it for all eternity.

Setting up Multipathing
The DL380's I worked on here had an additional 4 port NIC installed, for a total of 8 1Gb ports. The 4 on-board ports I dedicated to the Service console, vmkernel et al, standard stuff. The 4 ports on the add-on NIC I used for iSCSI, perfect considering the AX4-5i also has 4 iSCSI ports. What I did then was set up a new vSwitch, added my 4 Nics to the vSwitch and then created 4 seperate VmKernel ports, so that we have a one-to-one mapping between the VMkernels and the NICs. Here's how to do that:

1. Create a new vSwitch that we're going to dedicate to iSCSI
2. Connect your NICs to this vSwitch by going vSwitch - Properties. Click the Network Adapters tab and click Add. Select your NIC's and click Next and Finish.
3. Now we create VMkernel ports for all our newly added adapters, like so: Go vSwitch - Properties and click the Ports tab and click Add. Select VMkernel, give it a nice label and a suitable IP address and click Finish. Create a VMkernel port for every adapter assigned to your iSCSI vSwitch.
4. Now the important bit, we're going to do the one-to-one VMkernel to NIC mapping: On the ports tab, select one of your new VMkernel port and click Edit.
5. Select the Nic Teaming Tab and check the Override vSwitch failover order
6. Make sure only one adapter is active, move all the other NIC's down to the Unused Adapters section
7. Rinse and repeat for every VMkernel port on your vSwitch

Alas, we're not done yet - now I'm going to introduce you to my little friend esxcli. This fun little guy will enable us to connect our newly created VMkernel ports to the ESX iSCSI initiator

Enable Software iSCSI Multipathing

1. From the CLI (console, ssh, pick your poison) run the following command esxcli swiscsi nic add -n vmk# -d vmhba33
2. Rinse and repeat for all your ports, verify your work by executing the following command: esxcli swiscsi nic list -d vmhba33
3. You can then rescan your iSCSI initiator via the vSphere GUI. You can also verify multpathing via the paths view for the vmhba33 adapter.

Happy Multipathing! It should be mentioned that iSCSI and Jumbo frames go hand-in-hand. I will do a post detailing that can of worms in the near future.