[DRBD-user] ocf:linbit:drbd: DRBD Split-Brain not detected in non standard setup

Dr. Volker Jaenisch volker.jaenisch at inqbus.de
Mon Feb 27 10:44:31 CET 2017

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Servus Lars!

Am 26.02.2017 um 19:39 schrieb Lars Ellenberg:
> From the Pacemaker PoV, all is good...
> Pacemaker won't indicate that the 3rd disk
> of your 8-disk RAID 6 is broken, either.
And that is IMHO in a way correct. Since if a failover to this faulty
node would be neccessary - it would not be perfect - but it would not be
a disaster.

In the case of DRBD connection loss it would lead IMHO either to a split
brain or a stalled HA system not taking action.
>
> But yes, I argued your point of view before myself as well.
Thanks for restoring my pride. :-).
>
> crm_mon -L will list negative location constraints
> ("xyz prevents foo from running on bla").
> DRBD and complaints like yours were the reason I implemented that.
>
> Also pacemaker learned about "degraded, but OK" monitoring
> status return codes (OCF_DEGRADED, OCF_DEGRADED_MASTER),
> intended purpose exactly only to "allow crm_mon to flash warning lights"
> (or any other consumer of the status section).
> Main reason for introducing these was, again, DRBD,
> and complaints like yours.
My intention was not to complain. I was just wondering about this
bahavior of pacemaker and liked to learn and discuss. And I learned a
lot - at least my limits :-)
>
> We just don't use those exit codes in our RA yet.
>
> Nor does anyone else, afaik. It has not even made it into
> ocf-returncodes in resource-agents yet.
>
> Probably, because they don't work, yet:
> even though CRMD and the policy engine and later consumers
> would treat them OK-ish (I think),
> LRMD choses to "filter" exit codes in ocf2uniform(),
> "just in case", so they will never make it back to CRMD
>
> I may have forgotten to file an issue there :-/
Should we address this topic on the pacemaker mailing list. I still
think it would be an important improvement.

Cheers,

Volker

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