I've followed the discussion in the thread. Is it possible to for example make configuration with: - two SMTP(Postfix)/POP&IMAP(maildb) servers in front; - two db servers(PostgreSQL) working in active-active (both read&write) configuration behind? I would like to have configuration in which failure of one of front or/and one of database nodes would not make the system unusable. Also I would like to use both database servers (read&write) during normal operation to share load beetwen them. Is it possible? I'm not a database professional so please excuse me if the question is fairly easy :)
You have written that one can use MySQL and read-only slaves. These slave servers can be used for handling read only user queries (POP&IMAP). I have a second question: POP&IMAP do not only make read operations, these protocols also support write operations (make a directory, remove a message, ... - as I think). So what is the purpose of read-only database host during normal operation (when active/master node is working properly)? As I see it now it can surely be used as a spare or for creating reports, are there more usage possibilities? Regards, Rafal. 2011/3/5 Reindl Harald <h.rei...@thelounge.net> > Am 05.03.2011 14:13, schrieb Stan Hoeppner: > > Reindl Harald put forth on 3/5/2011 6:02 AM: > > > > Thanks for the info. Need one clarification: > > > >>> Can you cluster the dbmail IMAP daemon on multiple external hosts to > >>> support thousands of concurrent IMAP users, without the locking > >>> contention of NFS or cluster filesystems, thus achieving lower latency > >>> and greater throughput? > >> > >> yes you can because you have only to install dbmail/postfix on all > >> of them with access to the same database, for postfix you > >> can use replication-slaves too as fallback > > > > I asked about multiple IMAP servers and you answered with Postifx, which > > is an SMTP server, not an IMAP server. > > it seems you did not read > i answered with "dbmail/postfix" > > dbmail = imap/pop3/lmtp/sieve > > postfix belongs to my answer because i would use one big db-server > and on the mail-hosts postfix/dbmail-imapd/dbmail-pop3/dbmail-lmtpd > sahring the same database and the point is that you can use > all this hosts as mx and imap-host because they have the same data > > using replication slaves for postfix is nice beacuse you can spread > the read-only-load away from the main-db-server > > > In the Dovecot world, for a high availability and high concurrent user > > load cluster, one may setup say, 12 low end 1U rack servers with 4GB RAM > > and dual GbE ports each, to handle about 5,000 concurrent IMAP users > > (~400 users each), with all 12 servers accessing the same high > > performance NFS mailstore. > > and in dbmail you use a hig-performance db-server > > > Dovecot can't use dbmail for message storage or indexes. > > dovecot is in context dbmail obsolete > but we use it as imap/pop3-proxy and for authentication > in front of dbmail because dovecot supports more auth-mechs > > > My question is how would one build such an IMAP cluster with dbmail? > > I would assume a dbmail IMAP server component would need to replace > Dovecot > > in this setup. Is such a thing possible? > > yes since dbmail is imap/pop3/lmtp/sieved > > > Apologies to all as this thread has wandered into OT territory. This is > > my last post on the subject. I just wanted to understand if/how dbmail > > can scale with both Postfix delivery and IMAP retrieval in a clustered > > setup. > > no problem, you did not realize that dbmail/mysqld is the whole > mail-system only needing an MTA like postfix or exim > >
