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List:       courier-users
Subject:    Re: [courier-users] RES:  Courier Backup / replication point
From:       gordan () bobich ! net
Date:       2007-11-26 10:26:02
Message-ID: Pine.LNX.4.64.0711261025230.2808 () skynet ! shatteredsilicon ! net
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This sounds very much like a re-invention of a wheel. If you need 
high-availability and load sharing on your mail system, then cluster the 
servers properly and set up a GFS file system on top of a SAN or if you 
don't have a SAN, on top of a DRDB. I have recently deployed just such a 
system. I cannot see any advantage to lifting this functionality up to the 
application level when a more generic solution already exists.

If you want to also share the root file system, look at the "Open Shared 
Root" project. If you don't want to do it based on SAN/DRDB and GFS, you 
can do it all based on NAS/NFS, but that still leaves you a single point 
of failure (NAS appliance, unless that is mirrored using something like 
NBD (cold spare) or DRDB (hot spare)).

Gordan


On Sun, 25 Nov 2007, Ronie Gilberto 
Henrich wrote:

> Hi Jérôme, Hi Jay,
>
>    The disadvantages in using something at the filesystem/block is
> specially regarding load balancing.
>    We have two servers, with different IP addresses inside our network,
> where courier is running.
>    At the front, we have the firewalls and LVS doing a load balancing. They
> will redirect to the active courier server.
>    So, if we replicate at the filesystem/block layers, we have to take out
> several files from the replication proccess, because the different IP
> addresses, different server names, and so on.
>
>    As a solution for that situation, I think that a "replication point"
> feature in courier will be a nice solution.
>
>    We have a software develop team, so we can do that contribution to the
> courier project.
>
>    Maybe we could improve this idea...
>
>        Best regards,
>
>        Ronie
>
>  -----Mensagem original-----
>  De: Jérôme Blion [mailto:jerome.blion@free.fr]
>  Enviada em: sábado, 24 de novembro de 2007 10:12 PM
>  Para: Jay Lee
>  Cc: ronie@ronie.com.br; courier-imap@lists.sourceforge.net;
> courier-users@lists.sourceforge.net
>  Assunto: Re: [courier-users] Courier Backup / replication point
>
>
>  Jay Lee a écrit :
>    Sounds to me like something that should be (and has been) configured at
> the filesystem/block layers rather than at the Courier application layer.
> Take a look at projects like RedHat's GFS or Sun's ZFS.  I don't know much
> about NetApps either but I know they do NFS very well (which Courier
> supports very well) and I'm pretty sure they can be configured redundantly.
>
>    Jay
>
>
>    On 11/24/07, Ronie Gilberto Henrich <ronie@ronie.com.br> wrote:
>
>              Is it any feature in courier that allows me to inform backup
> storage paths?
>
>              Today I use unison to maintain a replica of our email files,
> configurations, ..., in a second server to use as a fast recovery backup
> solution.
>              The problem is that unison uses a lot of resources and IO_WAIT
> is always very high.
>
>              So, I was wondering if it is any feature to inform backup
> storage paths for courier to save all its files always into two different
> paths. Does something like this exist?
>
>              If it does not exist, don't you think it is a interesting
> feature to be implemented?
>
>                      Thanks and regards,
>
>                      Ronie
>
>  Hi,
>
>  If we work with a filer, an easier way to proceed would be to affect
> LUNS/filesystems to the "backup" server.
>  This way, you don't have to copy anything...  The rollback on the master
> server just follows the same process.
>  After that, you have to secure your filer. (snapshot and so on)
>
>  HTH.
>  Jerome Blion.
>

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