[gpfsug-discuss] mmnetverify

[Simon Thompson (Research Computing - IT Services)]

It looks to run sequential tests to each node one at a time and isn't using NSD protocol but echo server.

We found some weird looking numbers that i don't quite understand and not in the places we might expect. For example between hosts on the same switch, traffic flowing to another switch and traffic flowing to nodes in another data centre where it's several switch hops. Some nodes over there were significantly faster than switch local nodes.

I think it was only added in 4.2.2 and is listed as "not yet a replacement for nsdperf". I get that is different as it's using NSD protocol, but was struggling a bit with what mmnetverify might be doing.

Simon

From: gpfsug-discuss-bounces at spectrumscale.org [gpfsug-discuss-bounces at spectrumscale.org] on behalf of Sanchez, Paul [Paul.Sanchez at deshaw.com]
Sent: 17 March 2017 19:43
To: gpfsug-discuss at spectrumscale.org
Subject: Re: [gpfsug-discuss] mmnetverify

Sven will tell you: "RPC isn't streaming" and that may account for the discrepancy.  If the tests are doing any "fan-in" where multiple nodes are sending to single node, then it's also possible that you are exhausting switch buffer memory in a way that a 1:1 iperf wouldn't.

For our internal benchmarking we've used /usr/lpp/mmfs/samples/net/nsdperf to more closely estimate the real performance.  I haven't played with mmnetverify yet though.

-Paul

-----Original Message-----
From: gpfsug-discuss-bounces at spectrumscale.org [mailto:gpfsug-discuss-bounces at spectrumscale.org] On Behalf Of Simon Thompson (Research Computing - IT Services)
Sent: Friday, March 17, 2017 2:50 PM
To: gpfsug-discuss at spectrumscale.org
Subject: [gpfsug-discuss] mmnetverify

Hi all,

Just wondering if anyone has used the mmnetverify tool at all?

Having made some changes to our internal L3 routing this week, I was interested to see what it claimed.

As a side-note, it picked up some DNS resolution issues, though I'm not clear on some of those why it was claiming this as doing a "dig" on the node, it resolved fine (but adding the NSD servers to the hosts files cleared the error).

Its actually the bandwidth tests that I'm interested in hearing other people's experience with as the numbers that some out from it are very different (lower) than if we use iperf to test performance between two nodes.

Anyone any thoughts at all on this?

Thanks
Simon

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