[ClusterLabs] Antw: Re: Antw: Re: EL6, cman, rrp, unicast and iptables

Noel Kuntze noel at familie-kuntze.de
Mon Sep 14 11:46:56 EDT 2015

Hash: SHA256

Hello Ullrich,

> What totem does it detect network problems when there are none:
> # grep ringid.*FAULTY /var/log/messages |wc -l
> 1981

Yup. What information from your specific setup can you contribute to this particular discussion
about Digimer's problem?

>> This is something that no other protocol you encounter on the internet/LAN
>> is supposed to do.
> Definitely not: 0 interface errors on any interface, not communication
> problems.

What does protocol error detection have to do with interface errors? Protocol errors aren't
contained in interface errors.

> Even NFS over UDP is much smarter than TOTEM is.
NFS over UDP is for bulk transfer of data. You're comparing apples to bananas.
What improvement for TOTEM do you want to take from NFS over UDP?
NFS over UDP has congestion control. Is it that what you mean?

> If you have a central authority that can decide on each eand every priority
> you are right. I was talking from practical experience...

In a point-to-point topology, like Digimer is using (host-switch-host), the
switch in between basicly guarantees that every valid frame that enters one port also exits
another port of the switch. This basicly makes the switch vanish here. It's no longer relevant for this,
assuming that it does its job and the switching matrix can handle the frames, which it probably does.
If it can not do that, then the switch should probably be replaced.

The remaining two points are the interfaces of the hosts.
Digimer uses bonds. So we have two interfaces on either side. The interfaces themselves do not do any prioritization.
They just pass valid frames through to the OS over interrupts. The central points now are the bonding devices,
which have traffic congestion control algorithms attached to them, too. Not for ingress, because Linux can't do it,
but for egress. The egress, as I deducted in other emails, is fine.
The pfifo_fast qdisc is the central point. There's nothing else in this architecture
that influences the transmission between the two points. Of course, this model is idealized.
Maybe there are outside factors that cause the problems, maybe there are not. This is something
I cannot know about this setup.

- -- 

Mit freundlichen Grüßen/Kind Regards,
Noel Kuntze

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