[DRBD-user] How to make a data backup on the secondary node?

Dominik Klein dk at in-telegence.net
Thu Nov 8 09:18:37 CET 2007

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

> Dominik, what you are attempting to do is possible by way of temporarily 
> suspending redundancy on your cluster. And deliberately inducing split brain. 
> If something goes wrong on your Primary in the meantime, you will not be able 
> to avoid a service interruption. If you're held liable for that, don't come 
> whining. 

I can live with the risc of something happening in the meantime.

My situation is as follows: I have a database's data directory on the 
drbd device. I saw a couple of times that - independent of drbd - 
database files may be corrupted for many reasons. In that situation, the 
secondary node wont help at all (correct me if I'm wrong, but I think 
I'm not). So I want to copy the files in a reasonable interval. As I 
can't copy the files while the database is running and I don't want to 
hit the primary with a dump of all data (load is high enough already), 
this might be a way of implementing this backup.

> If you're not scared yet, read up here for inspiration: 
> http://blogs.linbit.com/florian/2007/10/04/checking-your-secondarys-integrity/

Thanks for that hint.

> This will also tell you why a full resync is *not* necessary afterwards, 
> contrary to your earlier observation. :-)

I didn't know "discard my data". I used "invalidate" and *that* 
certainly does a full sync. But that's my fault.


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