[Dovecot] HA Dovecot Config?

[Rick Romero]

Quoting "Eric Rostetter" <rostetter at mail.utexas.edu>:

> Quoting Rick Romero <rick at havokmon.com>:
>
>> They claim to be real-time, and with kernel hooks into  
>> reads/writes, it seems promising to run on top of the OS..
>
> Yes, but that doesn't mean it will work in the cluster environment...
>
> It also says things like:
>
>> There are different types of file locks.  In addition to these differences,
>> each OS has its own set of rules regarding file locks as well.  FRP's
>> replication of locked files will vary in relation to the way the OS treats
>> these types.  However, one rule is consistent throughout all operating
>> systems in that exclusive file locks will prevent FRP from replicating data.
>
> See that last line there???  Want to bet something in the mail setup
> (MTA, dovecot, system jobs like backup, etc) put an exclusive lock on
> files from time to time?
>
> Again, a fine backup system, and depending on your needs it might be
> okay for a failover setup, but not for an active-active setup.  For
> that you need a lock manager, which they promise "in the future" but
> don't deliver yet...

I thought the entire reason (ok not the _entire_ reason but..) for  
Maildir was to avoid locks and allow easy concurrent access to a  
mailbox through many different applications.

 From DJB's page:  http://cr.yp.to/proto/maildir.html

Why should I use maildir?
Two words: no locks

So while I do agree that file locking is a possible problem in an  
active/active setup with FRP, I think it's possible - as long as the  
admin is aware of the risks. So for backup purposes, to avoid locks  
for example, use ZFS snapshots.

I'm not even a user of FRP at this point, but it's something that  
intrigues me for active/active because of it's OS independence.  I  
want ZFS.  I really enjoy ZFS. I already have active/passive with zfs  
sends, I want to step it up :)

Yes, there are definitely things to be aware of.  I'm not sure if this  
is the place to hash it out, but I think that while it's not a cheap  
solution it may fit MY environment - and possibly others who use  
Maildir.

I guess everyone is as cheap as I am and hasn't set it up yet :)

Rick