deepOfix Mail Server - A Clustering Concept

This is just a brief method on how to use deepOfix Mail Server in Clustering Mode. deepOfix can be setup to operate in Clustering Mode. However, there are no in-built features for doing that. We have done some setup of deepOfix in high-availability configurations, but we don't use ultramonkey or Linux HA services for that. This is how we try to solve the problem:

  • Setup two (or more) deepOfix servers - one is the master while others are designated as slaves.
  • Setup LDAP replication so that any modifications done to accounts on the master LDAP server reflect back to the slaves.
  • Setup a shared storage server where all the mailboxes are stored. Make thsi storage server available to all the deepOfix server in the cluster. That way they all write to the same storage volume. Since deepOfix uses the Maildir format for user mailboxes, concurrent access to the mailbox (by multiple deepOfix servers) is not a problem at all.
  • Configure multiple DNS records - for SMTP traffic, for IMAP / POP3 / Webmail access etc. For example, if IP1, IP2 and IP3 are the IPs of your servers, then mail.domain.name could point to all these IPs. Additionally, you would configure three MX records. Then whenever someone accesses SMTP or POP3 or IMAP server, they get directed to one of the three servers via simple round-robin DNS. The same thing happens for incoming email deliveries.
  • What happens if one of these servers fail? Well - the beauty of this solution is that all cluster members operate together, in real time and that failure is completely transparent to the operating environment of the mail server(s). If one of the servers go down and you get directed to it via DNS, you will fail to connect to it. In which case your mail client or browser (or someone else's mail server) should just go to the next available IP available via DNS.
  • The only problem with such a solution is the shared storage since it becomes a single point of failure. One way of getting past this problem is to use network block device (nbd) based solutions (like DRBD) or Storage Area Networks (SANs).

If you found this brief helpful to you. Please send acknowledgment at deepofix-users ( at ) list.deeproot.in. If you found any problem in this brief or any query regarding this please feel free to shoot out any question at deepofix-users ( at ) list.deeproot.in.