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

Ulrich Windl Ulrich.Windl at rz.uni-regensburg.de
Tue Sep 15 02:09:19 EDT 2015

>>> Noel Kuntze <noel at familie-kuntze.de> schrieb am 14.09.2015 um 17:46 in
Nachricht <55F6EBF0.2000504 at familie-kuntze.de>:

> 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
>>> 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.

If you send a protocol from A to B where neither A's interface nor B's
interface has any errors, and B reports a protocol error, the obvious
conclusion is that the protocol is broken. Es pecially if the protocol claims
to implement reliable in-order transfer.
Of cours from "no interface errors" you cannot deduce "no protocol errors",
but if both parties use the same software, the bad protocol can only come from
the software.

>> 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?

NFS over UDP has the feature that it works under load, even if some packets
are dropped. I cannot confirm that property for TOTEM.

>> If you have a central authority that can decide on each eand every
>> 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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