<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div><blockquote type="cite" class=""><div class=""><div class=""><blockquote type="cite" class="">With DNS this happens automatically because ips are rotated by resolvers<br class="">and the mailclient gets the same ip for all its connections. Failover<br class="">is builtin as mailclients just connect to the second ip when the first<br class="">is not reachable.<br class=""></blockquote><br class="">I don't trust DNS load balancing. I saw too many times a client stuck<br class="">with the wrong (down) IP... This is my experience ;-)<br class=""></div></div></blockquote><div><br class=""></div><div>Interesting, I have deployed that dns-based approach where two dovecot servers</div><div>are replicating between two distant datacenters. A few years ago one datacenter</div><div>had a major outage and new connections quickly failed over to the remaining</div><div>server. Maybe this is client specific and/or has improved over time.</div><div><br class=""></div><div>If the loadbalancer/director approach works for you, that's ok.</div><br class=""><blockquote type="cite" class=""><div class=""><div class=""><blockquote type="cite" class="">Replication works reliable with mdbox/sdbox but you should avoid maildir.<br class=""></blockquote><br class="">I'm using and I like Maildir. There are some documentation about to<br class="">don't use it with replication? Which are the drawbacks?<br class=""></div></div></blockquote><div><br class=""></div><div>Maildir is probably the most robust mail storage format, but it is very</div><div>demanding on your disks because flags like "Seen" are encoded in the</div><div>filename. Every flag change needs IO as well as copying/moving/deleting</div><div>mails, quota, ... A maildir with 100k+ mails can impact the servers overall</div><div>performance, but as you use all flash storage that may not be a problem.</div><div><br class=""></div><div>I remembered something about replication and maildir, took me some time</div><div>to find it:</div><div><br class=""></div><div><a href="https://dovecot.org/pipermail/dovecot/2017-February/107125.html" class="">https://dovecot.org/pipermail/dovecot/2017-February/107125.html</a></div><div><br class=""></div><div>Timo said (Mon Feb 20 10:09:48 UTC 2017):</div><div><br class=""></div><div>"<span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); white-space: pre-wrap; background-color: rgb(255, 255, 255);" class="">There seems to be something weird with using Maildir and replication.</span></div><div><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); white-space: pre-wrap; background-color: rgb(255, 255, 255);" class="">Haven't had time to debug it and it's likely not an easy bug to fix,</span></div><div><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); white-space: pre-wrap; background-color: rgb(255, 255, 255);" class="">so for now the solution would be to use only sdbox/mdbox with replication."</span></div><div class=""><br class=""></div><div>I don't know if that is still the case, I can just tell mdbox works for me.</div><div><br class=""></div><div><br class=""></div><div>Best regards,</div><div>Gerald</div></div></body></html>