[DRBD-user] Just restarting secondary causes split brain, can someone expain why please?

[David]

Lars Ellenberg wrote:
> / 2007-03-05 17:37:33 -0500
> \ David:
>   
>> So just starting drbd on hydrogen causes a split brain and oxygen, now the primary, to go into a standalone 
>> state.  Why is that?  The file system is mounted as a read only file system so no changes should be taking 
>> place. This is not a primary/primary setup so there is only one "active" node at a time. I was under the 
>> impression that the rebooting node, hydrogen, should see that it is out of date and become secondary, resync 
>> itself with the primary and stay in the secondary state until that is changed?  Am I wrong?
>>
>> Both systems are identical:
>> SLES 10
>> kernel 2.6.16.27-0.9-bigsmp
>> drbd 8.0.1 compiled from source
>>     
>
> I suspect that your reboot does disconnect the network,
> before it switches the drbd to secondary.
> so it would go
>    Primary/Secondary
> -> Primary/Unknown
> -> Secondary/Unknown
> -> Unconfigured.
>
> if so, the logs should tell you so.
> to fix it: get your stop scripts in the right order.
>
>   
Thanks, that solved the problem but brings me to some questions. 

Given a Primary/secondary setup, why is it that when a primary node that 
was improperly shut down comes back up, it does not see that it is 
invalid and out of date and instead of split braining, switch to 
secondary and just ask for a re-sync?


David