CentOS - Sep 2005 - Server Replication: CenOS, coda? lustre?

Hi list,
our lab is divided in two sites and we would like to have a clone of the 
mail server on the second site for redundancy only (used in case of a 
lost of connectivity with the primary mail server, with the MX entries 
in the DNS the clone will receive the mails instead). The problem(s) 
comes with the mail partition who must be replicated and synchronized 
over the time (and over the net) to the cloned mail server, so the users 
can still access their mails while we deal with the primary server. My 
search leads me to the coda FS (and maybe the lustre solution, but we 
only use opensource soft so it may only be the one year old version - 
which is open...).  Is there on the list people who are doing such 
things and if you are, can you give me some clues? What I think is 
something like a 'one read - multiple writes' FS who can handle the flow
of mails and securely replicates it to the clone server. Do we have no 
choice but to tolerate the lost of some emails when the  primary server 
stops responding? btw is it realistic?
Thanks,
Manuel

----- Original Message ----- 
From: "Manuel BERTRAND" <manuel.bertrand at lif.univ-mrs.fr>
To: "CentOS mailing list" <centos at centos.org>
Sent: Friday, September 16, 2005 7:10 AM
Subject: [CentOS] Server Replication: CenOS, coda? lustre?

> Hi list,
> our lab is divided in two sites and we would like to have a clone of the 
> mail server on the second site for redundancy only (used in case of a lost 
> of connectivity with the primary mail server, with the MX entries in the 
> DNS the clone will receive the mails instead). The problem(s) comes with 
> the mail partition who must be replicated and synchronized over the time 
> (and over the net) to the cloned mail server, so the users can still 
> access their mails while we deal with the primary server. My search leads 
> me to the coda FS (and maybe the lustre solution, but we only use 
> opensource soft so it may only be the one year old version - which is 
> open...).  Is there on the list people who are doing such things and if 
> you are, can you give me some clues? What I think is something like a
'one
> read - multiple writes' FS who can handle the flow of mails and
securely
> replicates it to the clone server. Do we have no choice but to tolerate 
> the lost of some emails when the  primary server stops responding? btw is 
> it realistic?
> Thanks,
> Manuel
>


I've been looking into a similar configuration for our mail/DNS servers. One
option I've considered is http://www.linuxha.net/index.pl . They've got
a
framework for using DRBD to maintain a replicated disk where only one node 
can be writing or reading from it at a time.  It doesn't have as many 
features as Coda or Lustre, but it seems far simpler to configure and 
administer.


Solving the inbound message problem isn't too bad as a standard backup MX 
configuration will accept mails and forward them to the primary once it 
re-appears, but the user's mail stores will be unavailable as long as the 
primary is down.

I welcome other's thoughts on the matter.