I have High availability cluster that configured with DRBD resource.
Master/Slave Set: RVClone01 [RV_data01]
Masters: [ rvpcmk01-cr ]
Slaves: [ rvpcmk02-cr ]
I perform a test that disconnect one of the network adapter that connect between the DRBD network interfaces (for example shutdown the network adapter). Now the cluster display statuses that everything o.k BUT the status of the DRBD when running "drbd-overview" shows in primary server:
[root@rvpcmk01 ~]# drbd-overview
0:drbd0/0 WFConnection Primary/Unknown UpToDate/DUnknown /opt ext4 30G 13G 16G 45%
and in the secondary server:
[root@rvpcmk02 ~]# drbd-overview
0:drbd0/0 StandAlone Secondary/Unknown UpToDate/DUnknown
Now I have few questions: 1. Why cluster doesn't know about the problem with the DRBD? 2. Why when I put the network adapter that was down to UP again and connect back the connection between the DRBD the DRBD didn't handle this failure and sync back the DRBD when connection is o.k? 3. I saw an article that talk about "Solve a DRBD split-brain" - https://www.hastexo.com/resources/hints-and-kinks/solve-drbd-split-brain-4-steps/ in this article it's explain how to get over a problem of disconnection and resync the DRBD. BUT how I should know that this kind of problem exist?
I hope I explain my case clearly and provide enough information about what I have and what I need...