[DRBD-user] Dual Primary Mode: Shared Directory blocked after node crash until reboot

DRBD User DRBDUser at gmx.at
Wed May 13 09:43:37 CEST 2015

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


found a way without fencing:

create /etc/dlm/dlm.conf and copy to all nodes

* To use no fencing, use this line:

enable_fencing=0



now if i pull the power plug it takes about 5sec and the other node continue to operate


Gesendet: Mittwoch, 13. Mai 2015 um 09:29 Uhr
Von: "DRBD User" <DRBDUser at gmx.at>
An: drbd-user at lists.linbit.com
Betreff: [DRBD-user] Dual Primary Mode: Shared Directory blocked after node crash until reboot
for manual ack i use these (RHEL7) :

dlm_tool fence_ack nodeid
 
 

Gesendet: Mittwoch, 13. Mai 2015 um 09:23 Uhr
Von: Digimer <lists at alteeve.ca>
An: "DRBD User" <DRBDUser at gmx.at>, drbd-user at lists.linbit.com
Betreff: Re: [DRBD-user] Dual Primary Mode: Shared Directory blocked after node crash until reboot
If you want automatic recovery of any sort, yes, it is required to avoid
a split brain.

On 13/05/15 03:00 AM, DRBD User wrote:
> So for a primary/secondary setup I have to deal with fencing/stonith too ?
>
> I am using RHEL 7 and i can't find the fence_ack_manual command (for test purposes) ?
>
>
>
> Gesendet: Mittwoch, 13. Mai 2015 um 08:40 Uhr
> Von: Digimer <lists at alteeve.ca>
> An: "DRBD User" <DRBDUser at gmx.at>, drbd-user at lists.linbit.com
> Betreff: Re: [DRBD-user] Dual Primary Mode: Shared Directory blocked after node crash until reboot
> On 13/05/15 02:36 AM, DRBD User wrote:
>> Ok i understand:
>>
>> In a dual primary setup without a valid stonith configuration i have to wait until the crashed node is set to a *known* state: eg. using reboot, manual intervention.
>>
>> But what if the crashed node never gets alive:
>> Will the stonith setup set the state of the crashed node to a *known* state, so that the active node can continue to operate ?
>> Or do I have to intervene manually ?
>>
>> So for my plan to have a high available service (which saves its state to a shared directory) a primary/secondary setup may be the way to go - or i is fencing/stonith always a must ?
>
> The cluster (and DRBD) will remain blocked indefinitely. The only way to
> resume operation is when fencing succeeds or a human tells DRBD that the
> lost node is offline (via manual intervention).
>
> As an aside; Red Hat used to support manual fencing, but dropped support
> for it when RHEL 6 was released in 2010. The reason was that, on paper,
> manual fencing sounds fine. In practice, it was often misused and lead
> to split-brains.
>
> Consider; A cluster is locked up, people are screaming and the poor
> admin is trying to remember what to after a year of not touching things.
> s/he remembers about manually clearing the fence and then does so
> without first verifying the last node was off/dead. Is such a case, you
> have a split-brain and all the potential damage that goes with it.
>
> Get hardware fencing. It is the only sane and sensible option.
>
> --
> Digimer
> Papers and Projects: https://alteeve.ca/w/
> What if the cure for cancer is trapped in the mind of a person without
> access to education?
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--
Digimer
Papers and Projects: https://alteeve.ca/w/[https://alteeve.ca/w/][https://alteeve.ca/w/[https://alteeve.ca/w/]]
What if the cure for cancer is trapped in the mind of a person without
access to education?
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