NPV feature needed?

[DrPepper1234]

Hello everybody,
here we have a director switch (MDS-9513) with NPIV and fport-channel-trunk features enabled.

We had following chain: 9513 -> 9124e (module from HP blade enclosure) -> VC FlexFabric (another HP blade enclosure).

MDS9124e also has got NPIV and fport-channel-trunk features enabled.

Now both blade enclosures have been moved to a different place, where topology is different, and where a Nexus 5K is in the middle; the Nexus has got NPV enabled.

Now we have this chain: MDS9513 -> Nexus 5K -> MDS9124 -> VC FlexFabric.

ISL from 9513 to N5K uses F ports on 9513 and NP ports on N5K
ISL from N5K to 9124e uses NP ports on N5K and F ports on 9124e
Ports from 9124e to FlexFabric are F port

The problem is that I don't see the 9124e in the fabric (it has disappeared from DCNM).
Do I need to enable NPV on the 9124e? And in this case, which port mode should I use?

I also have a problem: the MDS-9124e has disappeared from DCNM, and it's not seen by the fabric, while the N5K is there, with a dashed line (meaning NP link).

Thanks

[Walter Dey]

Do you have any reason to do NPV cascading ? doesn't make sense !

I would just convert the link between MDS and N5k to a regular ISL (E-Port, resp TE-Port) and it should solve your issue.

[DrPepper1234]

I don't have any reason to do cascading... it's only that I don't know very well how it works, because I'm pretty new to NPV mode. That's why I'm asking :-)

Anyway the N5K does not allow me to configure the port as E (or TE) port: the only options I have are F-port, SD-port and NP-port.

[Walter Dey]

I assume you are ok regarding licensing.

Most likely your N5K is in NPV mode, you should change this to FC switch mode ! attention, this requires a reboot and is disruptive.

conf t

no feature npv

[DrPepper1234]

That's exactly what I wrote at the beginning: N5K is in NPV mode.

Actually I can't remove NPV mode, because the switch is managed by a different group.

[Walter Dey · Accepted solution]

This N5k in NPV mode is totally useless ! convince this other team to convert to switch mode; I agree, it means one more switch in their FC fabric. And in addition, you would move the NPIV function from the MDS to the N5k; flogi happens now on N5k, not anymore on MDS.

[DrPepper1234]

This N5K is used also for network (ethernet), and I can try to talk to them, but most probably I will not convince them.

Is there a way to have my MDS9124e in the fabric with this N5K in NPV mode?

[Walter Dey]

Cascaded NPV is not supported, and as you experience, doesn't work ! Schedule a maintenance window and do a reboot/reconfigure of the N5k ! There is no other solution.

[DrPepper1234]

Ok... if there's no other solution I'll talk to them.

But now I'm wondering what's the purpose of NPV, if a switch with NPV is useless.

As far as I understand, as soon as you put an NPV-enabled switch in the middle, the SAN just stops there... completely useless.

[Walter Dey]

http://blog.scottlowe.org/2009/11/27/understanding-npiv-and-npv/

http://datacenteroverlords.com/2012/05/08/npv-and-npiv/

gives some nice clarification what NPV and NPIV is.

NPV-enabled switch is a misleading name. It's more a HBA aggregaor / concentrator. By no means a FC switch, therefore not part of the SAN !

I hope this clarifies your situation.

[DrPepper1234]

I understand what is NPV and NPIV, and I understand that it is not part of the SAN.

But still it is useless... I cannot plug a host to it, I cannot plug a storage to it, and I cannot plug an MDS switch to it.

Useless.

[Walter Dey]

I understand what is NPV and NPIV, and I understand that it is not part of the SAN.

Sorry, I don't think you understood what NPV is ?

But still it is useless... I cannot plug a host to it, I cannot plug a storage to it, and I cannot plug an MDS switch to it.

Sorry, you are wrong here. You can connect hosts to a NPV device, as well as connect a NPV device to a MDS switch.

MDS9513 (NPIV) -> MDS9124 (NPV) ->Hosts is a valid configuration

MDS9513 (NPIV) -> Nexus 5K (NPV) -> MDS9124 (NPV) -> Hosts is not valid !!!!

NPV was invented by storage industries when blade systems started to emerge and flood the datacenters. If each blade chassis has 2 FC switches, the number of FC switches in a SAN would explode, reaching the max. number of 255 very quickly ! and this was the major use case to introduce NPV, which is not a FC switch.

[DrPepper1234]

Ok, thanks for explaining.

In the same way I guess the following is not valid:

MDS9513 (NPIV) -> N5K (NPV) -> MDS9124 (NPIV) -> Host

In this case I really need NPV to be disabled from there.

[Walter Dey · Accepted solution]

Correct ! I would call this not useful ! although possible, whereas the chain NPIV-NPV-NPV is not valid. The concept of NPV is really to connect hosts, which below is not the case. In below case, hosts would be connected to MDS9124, and storage to MDS9513; however, the hosts would NOT see the storage.

MDS9513 (NPIV) -> N5K (NPV) -> MDS9124 (NPIV) -> Host

[DrPepper1234]

Great!

Thanks!