[Users] Zimbra doing similar like Exchange DAG

Naisiew Yeak yeak at md.com.my
Wed Nov 7 09:00:48 CET 2018


Hi Randy,

Thanks for the info.

About this “application layer consistency” issue, if mb1 mount /opt from
local disk and it crashed (didnt clean shutdown), will the next boot up
having consistency problem?

Thanks.


On Wed, 7 Nov 2018 at 1:29 PM Randy Leiker <randy at skywaynetworks.com> wrote:

> Naisiew,
>
> When running an active/passive Zimbra mailbox server configuration with
> external storage (Gluster, Ceph, etc.), there is usually no issue with the
> external storage maintaining a consistent replica at the storage layer.
> The issue becomes consistency at the application layer, which is within the
> Zimbra mailbox service itself.  As a simple example, lets say that you
> setup two Zimbra mailbox servers, mb1 and mb2, and they both have access to
> /opt on GlusterFS, but only one mailbox server is powered on, while the
> other is powered down, on standby.  Then one day, mb1 goes offline due to a
> hardware failure.  You then go to power on mb2 & start the Zimbra services
> from GlusterFS where you have /opt mounted.  Your mb2 server will treat the
> mailbox data as a crash consistent copy of the mailbox data, which is what
> I was describing in my last email.  This is because mb1 (when it failed)
> didn't cleanly shutdown.
>
> As another example, if you have two mailbox servers, mb1 and mb2, and you
> need to do hardware maintenance on mb1, you could do a normal, planned
> shutdown of mb1, then when it finishes shutting down normally, you could
> then safely power up mb2, and it would work fine.  A key requirement to
> making this work is that both mb1 & mb2 would have to have the exact same
> networking configuration (host name and IP address) at the operating system
> level to be seen as the same email server from your user's email clients.
>
> This is not the only way to accomplish an active/passive mailbox
> configuration, but it should give you some helpful pointers in the right
> direction to get you started.
>
>
> Randy Leiker ( randy at skywaynetworks.com )
> Skyway Networks, LLC
> 1.800.538.5334 / 913.663.3900 Ext. 100
> https://skywaynetworks.com <http://www.skywaynetworks.com>
>
> ------------------------------
> *From: *"Naisiew Yeak" <yeak at md.com.my>
> *To: *randy at skywaynetworks.com
> *Cc: *"users" <users at lists.zetalliance.org>
> *Sent: *Tuesday, November 6, 2018 9:54:23 PM
> *Subject: *Re: [Users] Zimbra doing similar like Exchange DAG
>
>
> Hi Randy,
>
> Thanks for sharing.
>
> 1. The GlusterFS can't ensure consistent replica between nodes? I actually
> hope that it will. Anyway I will test for Zimbra usage. Will report
> findings.
> 2. Zimbra X direction is out of my league for now. If there is no choice I
> will have to pick it up and learn it.
> 3. Yes I am thinking of similar idea where MySQL is one component by
> itself with cluster setup. But all this setup tear Zimbra design
> away. Upgrade will become an issue. I guess this is what Zimbra X is trying
> to solve.
>
> Anyone has good answer how to answer those people comparing Zimbra to
> Exchange DAG? Simply say we are not ready? Work In Progress?
>
> My current answer: DAG is resource hungry. Zimbra is slim. However we are
> working toward similar active/active mailstore and keep the resources low.
> Can?
>
> Any other idea?
>
> Thanks.
>
>
> On Wed, Nov 7, 2018 at 1:27 AM Randy Leiker <randy at skywaynetworks.com>
> wrote:
>
>> Hi Naisiew,
>>
>> It sounds like you are referring to two different configurations: an
>> active/passive mailbox server (mb1 fails over to mb1a), and an
>> active/active mailbox server.  For the active/passive mailbox server,
>> assuming that you use the default Zimbra install location of /opt/zimbra,
>> and have /opt mounted from network storage, in this case GlusterFS, that
>> should work, but you should be aware that when the day comes that you need
>> to do a fail-over from mb1 to mb1a (assuming it's an unplanned fail over),
>> what you will end up with is a crash-consistent fail-over.  This means that
>> when mb1a mounts the /opt volume & begins attempting to start-up the
>> various Zimbra mailbox services, you will see complaints in the log files,
>> such as /opt/zimbra/log/mysql_errors & /opt/zimbra/log/mailbox.log about a
>> recovery from an unexpected shutdown.  This does not always work, and
>> sometimes Zimbra services, particularly the mailboxd service, fails to
>> start because MariaDB cannot recover or there is corrupt data in one or
>> more mailboxes.  The likelihood of recovery depends on how busy you
>> rmailbox server is.  The more busy it is with disk writes, the more likely
>> it is it may not be able to self-recover from a crash consistent copy of
>> the /opt data on GlusterFS.  To recover, you may then find you need to use
>> the procedures outlined here:
>> https://wiki.zimbra.com/wiki/Mysql_Crash_Recovery .
>>
>> In the current Zimbra 8.8.x version, it does not have a means to run in
>> an active/active configuration out of the box.  This is because data on the
>> mailbox server is very stateful, such as the mailbox blobs, the mailbox
>> indexes, the MariaDB database, and the redo log file.  This capability is
>> on Zimbra's road map, but the earliest version it is expected to appear is
>> within Zimbra X, which is the next major release of Zimbra.  In Zimbra X,
>> it contains an architecture change where all Zimbra services will run as
>> Docker containers, which will be orchestrated using Kubernetes.  Zimbra X
>> will only contain a subset of the features of the current Zimbra 8.8.x
>> version, with additional features being added, as demand requires.
>>
>> But, not all is lost.  For much of this year, I've been working
>> periodically on an open source project to add active/active capabilities to
>> the 8.8.x version.  In theory, it should also work on earlier 8.x releases
>> too, but I haven't tested it outside of 8.8.x yet.  So far, I have an
>> active/active Zimbra cluster working, which uses other open source products
>> to extend the shipping version of Zimbra 8.8.x.  It relies on abstracting
>> the storage of the mailbox server data in to Ceph, along with deployment of
>> MariaDB's Galera Cluster.  I don't have a web site setup for the project
>> yet, but as it gets closer to a deployable status, I'm giving occasional
>> updates on it on the weekly Zeta Alliance calls, and will likewise post
>> updates to this mailing list too.
>>
>>
>> Randy Leiker ( randy at skywaynetworks.com )
>> Skyway Networks, LLC
>> 1.800.538.5334 / 913.663.3900 Ext. 100
>> https://skywaynetworks.com <http://www.skywaynetworks.com>
>>
>> ------------------------------
>> *From: *"Naisiew Yeak" <yeak at md.com.my>
>> *To: *"users" <users at lists.zetalliance.org>
>> *Sent: *Tuesday, November 6, 2018 4:30:50 AM
>> *Subject: *[Users] Zimbra doing similar like Exchange DAG
>>
>> Hi there,
>>
>> Does anyone know how Zimbra can compare to Exchange DAG?
>>
>> I am planning to deploy GlusterFS to replicate my /opt to 3 nodes (one
>> arbiter). Any advice for this kind of setup? I actually do it on the
>> mailstore itself. Basically 3 mailstore servers, mb1, mb1a, mb1b. The mb1
>> is production and mount the volume to /opt. The mb1a has a copy of data and
>> ready to start up. Finally mb1b as quorum.
>>
>> I hope to run mb1 and mb1a Active/Active. That mean the mariadb should be
>> active/active on both of them. Current Zimbra is not ready for this right?
>>
>> I am searching for information what is the direction of the new
>> architecture for new Zimbra. Hope someone can share and let me know. I want
>> to begin deploy such foundation for my Hosted Zimbra service. Also use it
>> as demo platform for customer who is asking about Active/Active mailstore
>> (they literacy bring up DAG to compare).
>>
>> Thanks.
>>
>> --
>> Naisiew Yeak
>> +60 12 5067818
>>
>>
>> *Zimbra • Linux • SSL*
>>
>> My Directory Sdn Bhd
>> E-2-22, IOI Boulevard, Jalan Kenari 5, Bandar Puchong Jaya
>> <https://maps.google.com/?q=Jalan+Kenari+5,+Bandar+Puchong+Jaya+47170+Puchong,+Selangor,+Malaysia&entry=gmail&source=g>
>> 47170 Puchong, Selangor, Malaysia
>> <https://maps.google.com/?q=Jalan+Kenari+5,+Bandar+Puchong+Jaya+47170+Puchong,+Selangor,+Malaysia&entry=gmail&source=g>
>> .
>>
>>
>>
>>
>
> --
> Naisiew Yeak
> +60 12 5067818
>
>
> *Zimbra • Linux • SSL*
>
> My Directory Sdn Bhd
> E-2-22, IOI Boulevard, Jalan Kenari 5, Bandar Puchong Jaya
> <https://maps.google.com/?q=Jalan+Kenari+5,+Bandar+Puchong+Jaya+47170+Puchong,+Selangor,+Malaysia&entry=gmail&source=g>
> 47170 Puchong, Selangor, Malaysia
> <https://maps.google.com/?q=Jalan+Kenari+5,+Bandar+Puchong+Jaya+47170+Puchong,+Selangor,+Malaysia&entry=gmail&source=g>
> .
>
>
>
> --
Naisiew Yeak
+60 12 5067818


*Zimbra • Linux • SSL*

My Directory Sdn Bhd
E-2-22, IOI Boulevard, Jalan Kenari 5, Bandar Puchong Jaya
47170 Puchong, Selangor, Malaysia.
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