[DRBD-user] Dual-primary to single node

Digimer linux at alteeve.com
Tue Jan 17 19:43:38 CET 2012

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


On 01/17/2012 01:09 PM, Luis M. Carril wrote:
> 
> El 17/01/2012 18:56, Digimer escribió:
>> On 01/17/2012 12:32 PM, Luis M. Carril wrote:
>>> Hello,
>>>
>>>       Ok, the fencing and splitbrain mechanisms only enter to play when
>>> both nodes meet again after some failure.
>>>       So... meanwhile the nodes doesn´t connect their peer they disallow
>>> IO to the volume?
>>>
>>> Regards
>> No, if both nodes go Standalone and Primary, both will allow access to
>> the underlying storage, which results in a split brain. Fencing kills
>> one of the nodes (either the defective one or the slower one) preventing
>> it from changing it's underlying storage.
> Umph, but actually I'm testing to drop one node meanwhile it is writing
> in the volume, and the volume in the surviving node is stalled
> (drbd-overview freezes, but /proc/drbd shows
> that it is WTFConnection, Primary and Uptodate), even if I make drbdadm
> disconnect manually to make it go StandAlone, IO operations freeze on
> the directory.
> 
> Maybe is an issue related to OCFS...

Possibly, I use GFS2, not OCFS, so I can't speak to it's behaviour.

I can say though that GFS2 will also block when a node it the cluster
disappears, and it will remain blocked until it gets confirmation that
the lost node was fenced. This is by design, as a hung cluster is better
than a corrupted one. :)

-- 
Digimer
E-Mail:              digimer at alteeve.com
Freenode handle:     digimer
Papers and Projects: http://alteeve.com
Node Assassin:       http://nodeassassin.org
"omg my singularity battery is dead again.
stupid hawking radiation." - epitron



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