On Thu, Apr 05, 2007 at 04:28:02PM +0100, Mark Rogers wrote:
Any reason why the following won't work? It sounds too "easy"...
Server A is the primary DNS for a domain, and hosts its website, its database, and its email (SMTP in, dropped to POP3 mailboxes via spamassassin). All relevant records are in the DNS: www., pop3., etc, and point to Server A.
Server B is the secondary DNS for a domain, but all the records (www./pop3./etc) point to Server B (not A). Server B has an exact copy of the website, the database (synchronised through MySQL replication), and drops any email it receives through its own spamassassin into its local POP3 mailboxes.
...
In normal use, the domain resolves to server A and server B just acts as a redundant backup. If/when server A fails, its DNS vanishes and so clients request from the DNS on server B
That's not the way DNS works. Servers are returned in a random order and the concept of "primary" and "secondary" is more accurately described as "master" and "slave" - the primary is the server all the secondaries slave from, but it's not the first server that will necessarily be tried to lookup a host.
J.