mail server replication

[Paul Dekkers]

Gerard,

Gerard Ceraso wrote:

>I have a server setup using Cyrus 2.1 and postfix, with mysql. What I
>would like to have is 2 servers basically the second would be a
>replication of the first server. So I would like to be able to connect
>to either at any given time and get my mail and the mail being the same
>on both mainly for the reason if one was down. Anyone have a suggestion
>how I could accomplish this?
>  
>
I'm not sure about the perfect mechanism to achieve this. I think the 
best workable solution at this moment is to have a disk array with 2 
SCSI interfaces, and connect it to 2 machines. You can't mount a volume 
on both machines read-writeable, so it is impossible to connect to 
"either one". But at least you have a "hot spare" in case something 
happends with the OS or hardware of the first machine, and it is likely 
that your cyrus databases are still ok.

I once just synchronised the cyrus spool directory with something like 
unison, and that was not really the best solution. This bi-directional 
synchronisation works for plain files, but with the database files this 
causes more pain. I assume this works as soon as you reconstruct your 
mailboxes on the failover machine at a crash: at least you have all the 
data "stand by" on another machine.

It would be a bit better if there was something like offlineimap that 
could synchronise a complete spool. With offlineimap you can synchronise 
between two IMAP servers on user-basis. Maybe if offlineimap is 
modified, or if you setup a configuration for each user, you can achieve 
a situation with two identical mail-servers (where you can actually use 
both at the same time).

I hope this kind of functionality comes into cyrus once; I assume it is 
not there yet, I once asked this on the list before ;-) And maybe it 
shouldn't be too difficult, since there is already a synchronisation 
mechanism for NNTP in place, if I'm correct.

Regards,
Paul

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