FC port channels between MDS and UCS FI best practice?

[mbaak]

Hi,

We would like to create FC port channels between our UCS FI's and MDS9250 switches.

At the moment we have 2 separate 8Gbps links to the FI's.

Are there any disadvantages or reasons to NOT do this?

Is it a best practice?

Thanks.

[Walter Dey]

I assume your UCS FI's are configured with FC End Host mode (=NPV) and your MDS in NPIV mode.

In this case, port channel between FI and MDS is best practise.

On the MDS you need to enable

feature fport-channel-trunk

feature npiv

see eg. it's old, but essentially still valid

https://supportforums.cisco.com/sites/default/files/legacy/9/9/2/53299-UCS_1-4-1_F-port_channel-trunk-v1.pdf

[DavidHolm]

We run the FI in FC switching mode and connect to MDS 9148(NPV &NPIV disabled). Should i use Portchannel for FC connectivity?

We use IBM v5030 storage that is connected to the MDS but i can not find out if i can configure it with Portchannel. The IBM and FI both support 16Gb FC but the MDS. Is there a good way to configure this or should a buy new MDS 9148s(16Gb FC)?

[Walter Dey]

Hi David

Why are you running UCS FI in FC switching mode ?

95+ % of all UCS installations are running FI in FC End host mode ! (most customers running UCS FC switch mode, just wanted to save Investments in FC switches; typically a test / SMB Environment)

Just be aware, that the FC switch implementation on the UCS FI is not 100% compliant with the MDS SAN OS.

Therefore my advice: do UCS FC end host mode, and Port trunking / channeling between UCS FI and MDS.

[jihicks]

As Walter said, having port-channels is best practice.  Here is a little more information on why.

Let's take your example of two 8Gbps links, not in a port-channel ( and no static pinning ) for Fibre Channel connectivity:

Hosts on the UCS get automatically assigned ( pinned ) to the individual uplinks in a round-robin fashion.

(1)If you have some hosts that are transferring a lot of data, to and from storage, these hosts can end up pinned to the same uplink and could hurt their performance. 

In a port-channel, the hosts are pinned to the port-channel and not individual links.

(2)Since hosts are assigned to an individual link, if that link goes down, the hosts now have to log back into the fabric over the existing working link.   Now you would have all hosts sharing a single link. The hosts will not get re-pinned to a link until they leave and rejoin the fabric.  To get them load balanced again would require taking them out of the fabric and adding them back, again via log out, power off, reload, etc...

If the links are in a port-channel, the loss of one link will reduce the bandwidth of course, but when the link is restored, no hosts have to be logged out to regain the bandwidth.

Best regards,

Jim