dovecot - Jun 2014 - What are the options for HA and\or replication and\or storage?

I am considering couple options of converting a current service into a 
HA using multi servers or any other solutions.
The point is that I am thinking about the options and which I am looking 
for.
NFS can be a storage which has it's own pros and cons.
There is the option of DRBD but as of now it's limited for two hosts.
What options do exist out-there as a solution?

The main issues are that the current service is based on Maildir and is 
on one server with resierfs.
The service is composed of one host with 50k users couple disks in raid6.
On the same machine we have postfix as mailer.

I would like to hear about HA environment that I can use to replicate 
the boxes.

My basic research leaded me to smtp on one host or more and using lmtp 
to send the messages to dovecot o another host which will have a 
replicated host and will be used with storage system based on ISCSI or NFS.

Any other idea to enhance the current one or to replace it is more then 
just welcome.

Thanks,
Eliezer

Well, we are trying to do the same, dovecot has this ability, it's called
"dsync replication" (http://wiki2.dovecot.org/Replication)
It does his job, since it just sends incremental changes to the peer, so
it's very fast and low bandwidth consuming..

But I am having some problems when sieve scripts are being used; I'm trying
to understand what could cause the problem..
DRBD in sync configuration could be too slow, in async too dangerous..


> -----Urspr?ngliche Nachricht-----
> Von: dovecot [mailto:dovecot-bounces at dovecot.org] Im Auftrag von Eliezer
> Croitoru
> Gesendet: Donnerstag, 5. Juni 2014 17:09
> An: dovecot at dovecot.org
> Betreff: [Dovecot] What are the options for HA and\or replication and\or
> storage?
> 
> I am considering couple options of converting a current service into a HA
> using multi servers or any other solutions.
> The point is that I am thinking about the options and which I am looking
for.
> NFS can be a storage which has it's own pros and cons.
> There is the option of DRBD but as of now it's limited for two hosts.
> What options do exist out-there as a solution?
> 
> The main issues are that the current service is based on Maildir and is on
one
> server with resierfs.
> The service is composed of one host with 50k users couple disks in raid6.
> On the same machine we have postfix as mailer.
> 
> I would like to hear about HA environment that I can use to replicate the
> boxes.
> 
> My basic research leaded me to smtp on one host or more and using lmtp to
> send the messages to dovecot o another host which will have a replicated
> host and will be used with storage system based on ISCSI or NFS.
> 
> Any other idea to enhance the current one or to replace it is more then
just
> welcome.
> 
> Thanks,
> Eliezer