[DRBD-user] primary/primary with OCFS2 for the first time, questions

Christiaan den Besten chris at prolocation.net
Thu Mar 27 11:40:11 CET 2008

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


You describe a "split brain" situation. Read the documenation on  
possible recovery scenario's .... in the end it means you have to  
choose one primary to 'win', the other will loose its changes ...

I do remember having read about some 'future'work' on combining data,  
but this is not yet in any live code as far as I know.... (remember,  
drbd is block based, it doesn't know anything about the filesystem on  
top of it .... )


On Mar 27, 2008, at 9:30 AM, Martin Gombac wrote:

> Hi again,
> it's been 7 days and i haven't recieved any reply. Is my question  
> stupid, too obvious or what?
> Regards,
> M.
> On 2008.3.21, at 13:11, Martin Gombac wrote:
>> Hi DRBD users,
>> i've been using drbd since 0.6 version. I always used to setup fail- 
>> over clusters with primary/secondary and usually 2 drbd resources.  
>> Each running on one node as primary.
>> Now i'm thinking it's time to try primary/primary for the first  
>> time. I would use OCFS2 and gentoo.
>> I wonder how does OCFS2 or DRBD 8.0.* deal with failed failed  
>> replication link when the same file is accessed.
>> I mean, in the primary/secondary if the replication link went down  
>> on secondary no data was written. If for some strange reason the  
>> secondary resource became primary and mounted if we got split  
>> brain, solution was pretty straight forward. Data got  
>> (automatically or manually) replicated back from first primary node  
>> or the node with most current data on resource basis. r1 could be  
>> replicated one way, while r0 was in the other way.
>> But what happens when i have only one resource in primary/primary  
>> and the same file gets written to or created on both with different  
>> content while resource is disconnected?
>> I cannot say sync from first to second node since each node has  
>> some of the data correct and doing this in either way would make me  
>> loose half of the data. I'm I not understanding something here or  
>> is this expected? Maybe point me to some manual which explains drbd  
>> in primary/primary mode. I don't think i can find this info on: http://www.drbd.org/users-guide/index.html
>> Regards,
>> M.
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