Binding the ESX Software iSCSI Initiator to Two (or more) VMkernel Ports

benbuiltpc

We're troubleshooting an ESX 4.1 stability issue at work. We've had our hosts completely lock up, at seemingly random times, apparently due to a multipathing issue with iSCSI. We're running a Dell MD3200i SAN. While researching/troubleshooting this issue we've come across the concept of binding vmk's to the iSCSI software adapter:

Binding the ESX Software iSCSI Initiator to Two (or more) VMkernel Ports | A Sys Admin Blog

I understand how to do this, but I don't understand why. I've been doing some tests with and without the bindings, and I seem to get proper load balancing either way. So I'm not convinced that not specifying the bindings will lead to stability issues.

dave330i

http://www.vmware.com/files/pdf/techpaper/vmware-multipathing-configuration-software-iSCSI-port-binding.pdf page 3.

http://www.dell.com/downloads/global/products/pvaul/en/md-family-deployment-guide.pdf page 20.

meadIT

If you don't bind the NICs, what can happen is multiple vmkernels can use the same NIC. For example, vSwitch1 has vmk0 and vmk1, and uplinks pNIC1 and pNIC2. With the default load balancing, it's possible for both vmk0 and vmk1 to use pNIC1. If you leave the default NIC Teaming, it can confuse some storage arrays because it sees the traffic from the same IPs coming from the different MAC addresses. This can also affect arp tables in the switches they are connected to. By binding the vmkernels, it ensures consistency in where the data originates. You can almost think of it as turning each pNIC into a hba.

Which version of firmware are you running on the MD3200i SAN? Is it up to date? If I recall correctly, they fixed some multipathing issues in one of their releases here in the last 6 months or so.

benbuiltpc

Ok, I'm getting a better picture now. What if we only have 1 vmk port and 1 nic per vswitch? Could there be MAC address corruption in that case?

Thanks for the reminder on the firmware, I see that the latest one (released last week) does address iSCSI stability!

jibbajabba

This is what we are doing ...

One vSwitch > One vmkernel > One NIC

And then we configure the multipathing that way .. There are no MAC address issues .. you just have to make sure those two uplinks are in a portchannel on the switch (physical switch that is).

dave330i

jibbajabba wrote: »

This is what we are doing ...

One vSwitch > One vmkernel > One NIC

And then we configure the multipathing that way .. There are no MAC address issues .. you just have to make sure those two uplinks are in a portchannel on the switch (physical switch that is).

Interesting. Any particular reason it was built that way?

blargoe

^Yeah. Binding the vmk to the iSCSI software adapter is pretty trivial.

meadIT

blargoe wrote: »

^Yeah. Binding the vmk to the iSCSI software adapter is pretty trivial.

Even more so in vSphere 5. It's all in the GUI.