Dovecot HA/Resilience

[Jean-Daniel]

If you just want active/standby, you can simply use corosync/pacemaker as other already suggest and don’t use Director.
I have a dovecot HA server that uses floating IP and pacemaker to managed it, and it works quite well.

The only real hard part is having a HA storage.
You can simply use a NFS storage shared by both servers (as long as only one has the floating IP, you won’t have issue with the same client accessing it from both servers), but the storage will then be a single point of failure.
You may have both server have their own storage and sync it using dovecot replicator (I have never tried, so I can’t say for sure), or have an other layer taking care of the storage sync (like DRDB).

While drdb is fine to sync dovecot storage, it may not be enough if you really want HA and have other services (postfix, rspamd, …) running on that server, as you may need to also have the postfix queues (or other data) sync on both servers.



> Le 10 janv. 2020 à 21:12, Adrian Minta <adrian.minta at gmail.com> a écrit :
> 
> Yes, but it works for small systems if you set IP source address persistence on LB or even better, if you set priority to be Active/Standby. I couldn't find a good example with dovecot director and backend on the same server, so adding another two machines seems overkill for small setups.
> 
> If someone has a working example for this please make it public !
> 
> Quote from https://wiki2.dovecot.org/Director
> 
> "Director and Backend in same server (broken)
> NOTE: This feature never actually worked. It would require further development to fix (director would need to add "proxy" field to extra fields and notify auth that the auth_request can be freed)."
> 
> Also:
> 
> https://dovecot.org/pipermail/dovecot/2012-May/135600.htm
> 
> https://www.dovecot.org/list/dovecot/2012-June/083983.html
> 
> 
> On 1/10/20 8:09 PM, Aki Tuomi wrote:
>> Also you should probably use dovecot director to ensure same user sessions end up on same server, as it's not supported to access same user on different backends in this scenario.
>> 
>> Aki
>> 
>>> On 10/01/2020 19:49 Adrian Minta <adrian.minta at gmail.com> wrote:
>>> 
>>> 
>>>  Hello,
>>>  you need to "clone" the first server, change the ip address, mount the same maildir storage and use some mechanism to share the accounts database.
>>> 
>>>  Then you need to put a TCP load-balancer in front of the servers an you are good to go. This is the easiest solution if you already have in the network an appliance that can do LB. For instance if you already have a firewall with that function.
>>> 
>>>  
>>> 
>>>  Another solution is to make a cluster with corosync/pacemaker out of the two servers:
>>> 
>>>  https://www.digitalocean.com/community/tutorials/how-to-create-a-high-availability-setup-with-corosync-pacemaker-and-floating-ips-on-ubuntu-14-04
>>>  https://linuxacademy.com/blog/linux-academy/configure-a-failover-cluster-with-pacemaker/
>>> 
>>>  
>>> 
>>>  
>>> 
>>>  On 1/10/20 7:16 PM, Kishore Potnuru wrote:
>>> 
>>>  
>>>> Thank you all for the replies....
>>>>  
>>>> 
>>>>  I have the test environment with the same configuration. But I have been asked to go with same environment for HA/Resilience in Live.
>>>>    Yes, I have only one Live server. It is configured in "Maildir" format. The data stores on a Network / Shared Storage (But definitely not local disk, its a mount point).
>>>>    I have been asked to create a HA/Resilience for this environment. They gave me another server with same ram/cpu/os and I need to configure the dovecot on it.
>>>>    Please provide your suggestions/steps as I am new to this kind of environment.
>>>>    Is it possible, when any email comes to any one or both of the two servers, how it will be read by the user from Outlook? How to create the environment?
>>>>  
>>>> 
>>>>  Thanks,
>>>>  Kishore Potnuru
>>>>    On Fri, Jan 10, 2020 at 7:55 AM Sami Ketola <sami.ketola at dovecot.fi> wrote:
>>>> 
>>>>  
>>>>>    > On 10 Jan 2020, at 9.20, Emmanuel Dreyfus <manu at netbsd.org> wrote:
>>>>>  >
>>>>>  > On Fri, Jan 10, 2020 at 09:07:24AM +0200, Aki Tuomi wrote:
>>>>>  >> Replication is not supported with mbox. Most features are not.
>>>>>  >
>>>>>  > It would be nice if the document about replication could tell
>>>>>  > what setup works.
>>>>>      First step in setting up HA system would be to migrate away from mbox.
>>>>>    Sami
>>>>>  
>>>  -- 
>>> Best regards,
>>> Adrian Minta
>>> 
>>> 
>>> 
> -- 
> Best regards,
> Adrian Minta
> 
>