N5K - N2K Image Upgrade Single vs Dual Homed

[dumlutimuralp]

Hi,

The upgrade distuptive behaviour is not explained well in the following documentation link . Especially about single homed FEX topology.

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/upgrade/503_N1_1/n5k_upgrade_downgrade_503.html

1. I have just upgraded a dual homed Active / Active N2K to N5K environment as below. The downtime was exactly explained as above URL, just the time to reload the FEXs. Which was about 1.5 minutes or so...

Or should we NOT reload all the FEXs almost simultaneously by manual command (as mentioned in the upgrade guide) in this topology, in order to minimize the downtime ?

2.However I am curious if there would be any downtime in a single homed FEX topology as below. My guess is there would be just the downtime for the edge server to distribute the traffic to the other N2K.

I guess if the downtime is really a biggy,  then the second topology is easier to manage.

Comments area very much appreciated.

Dumlu

[Colby Beam]

I am not able to see the images you attached, could you please try reinserting them?

Also if I am understanding your question correctly, you are wanting to know if there will be downtime, if you upgrade a N5K with a 2K single homed. I assume you meaning something similar to this?

If so, yes the single home fex would be reloaded per the document it states: "Upgrade the first vPC switch (vPC primary switch) -  during this upgrade, the switch will be reloaded. When the switch is  reloaded, any dual-homed FEX will not be reloaded.  Only singled-homed FEXs are reloaded. Servers connected to these  dual-homed FEXs retain network connectivity via the second (vPC  secondary) switch"

[dumlutimuralp]

Hi,

I have uploaded the images once again. I know single homed FEXs will reload in the topology you attached. Actually that is why I might choose that topology, because since I could dual attach hosts to the single homed FEXs and also I could port channel the server to those two FEXs.

But if I use a a dual homed FEX topology then I can not port channel the server to two FEXs. So in a dual homed FEXs topology when I perform an upgrade, eventually I have to reload all FEXs to, I could reload them non sequentially one by one, but even in that case server to network traffic will experience short interruptions, at the times the traffic will switch to one NIC to the other on the server (while I reload the FEXs)

So I guess the single homed topology seems a better choice.

[Ruhann Du Plessis · Accepted solution]

The CCO document suggests reloading all FEXs at once with Dual-FEX scenario. It personally prefer doing it a FEX  a time. That was is more controlled, and traffic shift is more predictable. But boths works. Downtime is minimal to the hosts connected to the FEX.

Supporting dual-homed hosts to dual-homed FEXs is not yet supported. I was promised this is on the roadmap. So hopefully with the Jul release it will be added. (VPC-on-a-VPC)

But for the time being provided you dual-home your servers to two single homed FEXs your downtime should be almost none.  So stick with the single-homed FEX to N5K scenario, but port-channel your servers to 2x FEXs in a VPC.

hth