[DRBD-user] 3 way replication : promoting the "stacked" node

Lionel Sausin ls at numerigraphe.com
Tue Jan 11 12:07:26 CET 2011

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


Dear DRBD community,
We are setting up a 2+1 node cluster :
- A is master
- B is slave
- S is an additional spare/backup machine, disconnected most of the time
The use cases are :
- Normally we sync S once a week then unplug it and keep it safe. The 
dataset is big (26To) so it has to catch up fast.
- Of course when A fails we promote B
- But when either A or B fails, we still want HA: so we plug S in and 
keep it synced until the failed machine is repaired

So we intend to set up DRBD between A and B, and use a stacked DRBD 
resource to replicate (A+B) to S.

My question is: if A or B dies and can't be fixed, can S be reconfigured 
to replace it without a full sync?
In other words: can a setup like (A->B)->S be changed to (A->S) with a 
quick sync?

Thanks in advance if you can share your knowledge.

Lionel Sausin



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