Hi,
In order to reach a quorum after reboot, you need to have more than half
of yours mons running.
with 7 MONs I have to have at least 5 MONS running?
No. 4 is more than half of 7, so 4 would be a majority and thus would be
able to form a quorum.
4 would be more than the half but insufficient to reach a quorum.
I don't see why you think 4 would be insufficient.
But, would the cluster come up at all if I could get only 3 out of the 7
initial MONs up and running?
It wouldn't be able to form a quorum, and thus you would not be able to
use the cluster.
I.e. you have 2 mons out of 5 running for example - it will not reach a
quorum because you need at least 3 mons to do that.
Well, as I said, I had 3 MONs running, just the sequence in which they
came up after the reboot was odd,
The number 3 was specifically for the example of having 5 mons in total.
In your case where you have 7 mons in total, you need to have 4 running
to do anything meaningful.
The order they are started in does not matter as such.
And do I need to make sure that a quorum capable number of MONs is up
BEFORE I restart the OSDs?
No, that is not important. The OSDs will wait until the required number
of mons become available.
- stop MON / one after the other
- start MON / in reverse order, last shutdown is first boot
It is not required to stop or start mons in a specific order.
central question remains, do I need 5 out of 7 MONs running or would 3
out of 7 be sufficient?
The magic number here is 4.
--
Jens Kristian Søgaard, Mermaid Consulting ApS,
jens@xxxxxxxxxxxxxxxxxxxx,
http://wwww.mermaidconsulting.com/
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