hi,
i have a active mail server with amount of data ,now i want run another server for failover. on my research i have to use following software :
pacemaker + drbd
but i'm confused about how data replicated between these two server???
and if there is a better way please guide.

thanks.

hiiiiiii,
nobody knows about clustering , failover or something like this..................

If I can point you in the right direction, maybe use rsync (to sync the two mail stores?), or do a daily backup and restore of the DB if that is where you store your mail.

You have to setup a new MX record with your Name Server. Giving it a higher number then your primary server, it will then act as a backup. Here is more information on MX records.

With Linux there are SO many ways to get the job done... Personally, I try the hard way first so I understand the efforts a replicator application is saving me, and know a little bit of what runs in the background if I need to fix it...