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

Martin Gombac martin at isg.si
Fri Mar 21 13:11:55 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.

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 done 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 and 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:// 


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