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

[Noel Kuntze]

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Hello Ullrich,

> 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.

Agreed.

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

NFS is for bulk data transfer and has to deal with network saturation.
TOTEM isn't designed for this. Taking this from the first link[1]:
"The Totem single-ring protocol"
*Provides rapid detection of network partitioning and processor failure together with reconfiguration and membership services.

This property of TOTEM acts against the desired property of robustness against network
problems. I think the TOTEM configuration can be improved against
the known problems and sensitivity to datagram losses by increasing the retransmission timeout and threshold.
Doing this increases the time it takes for Corosync to detect dead nodes, though.

- -- 

Mit freundlichen Grüßen/Kind Regards,
Noel Kuntze

GPG Key ID: 0x63EC6658
Fingerprint: 23CA BB60 2146 05E7 7278 6592 3839 298F 63EC 6658

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