[DRBD-user] Using quorum in three node cluster results in split brain

[Markus Hochholdinger]

Hi,

I'm using drbd 9.2.2 and using the quorum feature together with the diskless 
node feature.
I've three nodes, A (perf1) and B (perf2) with a disk, C (perf3) without a 
disk.

Most of the time, the setup is behaving like expected. But in the following 
scenario, I get two primaries:
1. A is primary, B secondary, C is the diskless quorum.
2. A looses connection to B, i/o stops for around 10 seconds until A 
recognizes it can continue to be primary, i/o continues. B can't be promoted 
to primary. C sees both notes. B get its disk state to Outdated. All fine to 
this point.
3. A, now primary and i/o continues, looses connection to C. Nevertheless, A 
keeps primary (with the knowledge the outdated disk of B can't get primary).
4. B tries to get primary (mount drbd device) and gets primary as well! B sees 
C. Why doesn't C prevent this?
=> Now I've two primaries!

In my opinion, the Outdated secondary B shouldn't become primary, the quorum 
node C has the knowledge of the fact that A was primary and has changed data 
against the outdated secondary B.

Attached store1.res, the config of my resource store1.

Whre is my error? Is this expected with a diskless quorum? Why can an outdated 
secondary become primary? Any ideas?


Many thanks in advance,

-- 
Mfg

Markus Hochholdinger
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