Whether 'tis nobler in the mind to suffer not knowing the answer to this question or educate thy self…
Enough of Shakespeare... Where’s my PFE, when I need him? J
Well in previous releases of the operating system, customers always depended on vendors to provide a support solution for NIC Teaming software. Even then in those days, neither the vendors nor Microsoft supported teaming iSCSI Initiator and recommended using the vendor’s MPIO (multi-path I/O) solution and/or DSM (device-specific modules).
Now with the release of Windows Server 2012, we include our own version of NIC teaming software also known as Load Balancing/Failover (LBFO).
So here’s where the confusion comes in and a lot of customers have been asking us… Is NIC Teaming supported for iSCSI, or not supported for iSCSI?
So to demystify the question that inspired to write this blog, I consulted with Don Stanwyck (Sr. Program Manager / Windows Core Networking) who is the authority on this subject and here is the essence of the message he conveyed:
The Technet statement that basically quotes “iSCSI + NIC Teaming not supported” is still true for all teaming solutions, with the EXCEPTION of the Windows Server 2012 inbox NIC Teaming solution we provide.
If iSCSI Initiator is used with dedicated NICs such as in a stand-alone and/or Failover Clustering environment, then NIC Teaming should not be used (because it adds no benefit over MPIO for dedicated NICs).
If iSCSI Initiator is used in a shared NIC scenario (see figure below) such as in a Hyper-V 2012 environment, then iSCSI Initiator used over the Hyper-V switch (and over NIC Teaming) is supported.
In a native environment where the NICs are shared between iSCSI Initiator and other uses, the following configuration is also supported.
Just to make one point clear, the Microsoft’s Windows Server 2012 NIC Teaming (LBFO) solution is also supported for iSCSI targets (such as Microsoft’s iSCSI target) anytime, not just in the shared NIC scenario. So even if the iSCSI initiators aren’t using Microsoft’s NIC Teaming (LBFO) solution (and perhaps not MPIO/DSM either), the iSCSI targets can use teamed NICs however you like.
KEY IMPORTANT TAKE AWAY
When iSCSI is used with dedicated NICs, then using any teaming solution is not recommended and MPIO/DSM should be used. But when iSCSI is used with shared NICs, those shared NICs can be teamed and will be supported as long as it’s being used with Microsoft’s Windows Server 2012 NIC Teaming (LBFO) solution.
In addition, we will always recommend you consult with your iSCSI storage vendor to confirm the support of iSCSI solutions with their storage. When in doubt, you can always search the status of any hardware testing completed on the Windows Server Catalog - Certified for Windows Server 2012.