Are these wiki pages still valid for ZCS 7.x?
http://wiki.zimbra.com/wiki/Logger_(ZCS_6.0.x_and_later)
http://wiki.zimbra.com/wiki/Logger_(ZCS_5.0.x_and_earlier)
A) yes
Q) In a multi node environment, can I mix logger daemons (syslogd, rsyslog, syslog-ng)?
A) Yes, however you are likely to encounter compatibility problems;
http://bugzilla.zimbra.com/show_bug.cgi?id=67884
http://rsyslog.com/doc/v3compatibility.html
Q) TCP or UDP?
A) UDP is recommended since we have seen a tcp based syslog freezing a whole system.
Here is an interesting blog
http://blog.gerhards.net/2008/04/on-unreliability-of-plain-tcp-syslog.html
