I currently am running ZCS 5.0.14 32 bit (call it server A) with over 2000 users on Cent OS 5.2 32 bit edition. I have freshly installed ZCS 6 32 bit (call it server B) on another server machine with Cent OS 5.3 64 bit edition. Server B is a fresh install and thus doesn't have any users. Server A and B are right next to each other and can communicate with each other over the LAN. Now here's my plan. I wish to first migrate all users and mails from server A to server B and make server B my main mail server. Also I would like to install 64 bit Cent OS on server A and install Zimbra 6 on it (call this new configuration: server A$). Now, I would like A$ to be a fall back server just in case server B crashes, so I would want all my mail and users to be replicated on A$ from B i.e. I wouldn't want a user to know that server B crashed and so server A$ must contain all mails and user accounts as in B.
Please tell me how I can go about doing this kind of a migration.
Thanks and regards.