yes I know, you said that, but this does not help at all in my understanding what might go wrong.
I have to disagree here, for two reasons:
- my memcached servers are working. When I take a tcpdump I see that seafile stores and retrieves entries from all three memcache servers. Actually, in the tcpdump I see no connection errors that would correspond to the errors (SERVER MARKED DEAD) I see in seafile.log
- it is not true, that using a hot standby (as opposed to using an active-active setup using e.g. haproxy) implies manual work to do the failover. using a floating IP (and heartbeat for example) is enough two switch from one seafile app server to the other. so, by shutting down 2 of my 3 memcached servers I would actually loose HA. And I am not prepared to do that without a justified reason.
anyhow, I just updated my seafile servers to pro-6.2.4 and the errors seem to be gone.
thanks everybody for their help and suggestions.