[ClusterLabs] Reliability questions on the new QDevices in uneven node count Setups

Thomas Lamprecht t.lamprecht at proxmox.com
Mon Jul 25 09:29:54 EDT 2016

Hi all,

I'm currently testing the new features of corosync 2.4, especially qdevices.
First tests show quite nice results, like having quorum on a single node 
left out of a three node cluster.

But what I'm a bit worrying about is what happens if the server where 
qnetd runs, or the qdevice daemon fails,
in this case the cluster cannot afford any other loss of a node in my 
three node setup as votes expected are
5 and thus 3 are needed for quorum, which I cannot fulfill if the qnetd 
does not run run or failed.

So in this case I'm bound to the reliability of the server providing the 
qnetd service,
if it fails I cannot afford to loose any other node in my three node 
or also in any other example with uneven node count as the qdevice vote 
subsystems provides node count -1 votes.

So if I see it correctly QDevices make only sense in case of even node 
maybe especially 2 node setups as if qnetd works we have on more node 
which may fail and if qnetd failed
we are as good as without it as qnted provides only one vote here.

Am I missing something, or any thoughts to that?

best regards,

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