@olivierlambert thank you for the quick answer.
To be on the real safe side this means then a replication count not lower than 3 would be useful (from my perspective).
What would happen if a node of a 3 node cluster with replication count 3 (so all nodes have a copy) fails?
Would everything stop because replication count is higher than available nodes?
(I refer to post https://xcp-ng.org/forum/post/54086)