[DRBD-user] Guarantee write to both nodes

Digimer linux at alteeve.com
Fri Mar 19 13:15:19 CET 2010


On 10-03-17 06:35 AM, Yuri Ushakov wrote:
> Hello,
>
> Is it possible to block write to primary node when secondary is not
> available?
>
> That is, suppose PostgreSQL asks the filesystem to write some bytes. I'd
> like drbd to reply with "write OK" *only* if the data is written to both
> nodes. If secondary is unavailable because of network error, reply
> should be "not written".
>
> What I understood from reading the docs is that unavailable secondary is
> considered non-critical, and drbd continues writing to primary.
>
> Tested that as well - drbdadm disconnect resource, and primary can still
> write to mounted device.
>
> Can this behaviour be changed?
>
> Thanks for help,
> Yuri.

That would largely defeat the purpose of DRBD. When the second node 
disappears, the remaining node gets a "dirty" inode list in memory. When 
the node returns, it knows exactly what needs to be updated and syncs 
the missing data. This sync operation brings the other node back to 
being identical to the good node.

What, exactly, are you trying to accomplish?

-- 
Digimer
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