Direct connect NFS/CIFS with 1.4

Question

I see how 1.4's appliance ports can help with direct connect multipath iSCSI. Each fabric gets a VLAN/subnet, iSCSI has multiple targets via each fabric, etc.
But I don't see how appliance ports help with direct connect NFS/CIFS. E.g.,
In this diagram, traffic from hosts active on fabric B must go over the northbound LAN to reach the NAS. Even if every host and appliance has its NIC failover configured to prefer fabric A and perform preemption, you'll still have failures like NAS NIC's and IOM's that will cause some/all NAS traffic to go across the northbound LAN. Thus, you've got one of two situations:
    1) The LAN can handle the NAS traffic. If so, why not plug the NAS into the LAN in the first place?
    2) The LAN cannot handle the traffic, in which case you haven't built real fault-tolerance and, worse, a UCS problem can impact the LAN.
Am I missing something here? How are appliance ports better than using switch mode, shown below?

Answer 1

Yes - you have a valid point on the traffic pattern depending on what fails etc.
Just to back up for a moment..
Version 1.3 and below has 2 types of Ethernet ports - Uplink and Server port.
Version 1.4 has 4 types of Ethernet ports - Uplink, Server, Appliance, Monitoring port
In 1.3, to directly connecting a NAS to the FI's meant that you move to switch mode on the FI's and then set the port connecting to the NAS as an uplink port. What that did is that the port connecting to the NAS was a a trunk port at the FI end allowing all VLANs (i.e no VLAN filtering), no QoS settings etc.
So if you wanted to stay in End Host mode AND not liking the above caveats, you connected the NAS to an upstream switch and not UCS and that option remains wit you today.
What the appliance port gives you now is that the VLAN(s) the NAS belongs to can be filtered, QoS settings possible and most importantly, it works in End Host Mode (most deployments are based on it).
The above is the rationale for the Appliance port and the port type was neeeded even if it works today in switch mode.
Now the question comes, appliance port in EHM or Switch mode (which is what the question is).
In EHM you are right, east-west traffic between NAS-blades could utilize the upstream network.
You can design efficiently by specifying the fabric id (A or B as primary) or set fabric affinity if using a soft switch but  guaranteed total localization (not using upstream network) cannot be made as you correctly said depending on "what" fails.
If all the uplinks on A fail, yes the whole thing should fail over but if a link between the IOM and the FI fails, then the servers pinned to that link will start using the external network.
So yes, the network needs to be designed keeping the flows and what if scenarios in mind. East-west traffic not hitting upstream at all cannot be assumed.
The long term solution is to have data links between the FI's in EHM or they are vPC peers and hence both links to the NAS from the FI's will be active/active.
Appliance port in switch mode can be used but that also depends on which links are STP blocked etc to guarantee that.
The topology you mentioned does that ..but then you also need to keep in mind on failurea what happens etc i.e the ISL between the FI's should always be forwarding for that VLAN.
Thanks
--Manish