[Dovecot] is it necessary lmtp and director to avoid index corruption in mail delivery?

[mailing lists]

JF, thank you for the reply.

I'm just curious how to big players fix this problem, which seems impact systems with shared storage.

Have a nice day.



On 09/07/2011 12:59 PM, Jan-Frode Myklebust wrote:
> On Wed, Sep 07, 2011 at 11:26:28AM +0100, mailing lists wrote:
>> Hello all,
>> If I have several postfix/dovecot-lda boxes with shared nfs storage,
>> how director helps in this scenario?
> 
> The director can help by directing each unique user to the same backend
> server for each delivery, which should give you better performance
> (indexes cached in memory on only one machine instead of on all,
> inotify will work for IMAP NOTIFY), and also avoid some apparent race
> conditions that has lead to index corruption when several nodes are
> writing to the same mailbox at the same time.
> 
>> is it necesary to use lmtp instead of dovecot-lda?
> 
> Yes.
> 
> 
>> With postfix/dovecot-lda boxes incoming mail happens at the smtp layer
>> but director redirects are working in the lmtp/imap/pop3 layer.
> 
> Right.
> 
> With LMTP you can have dovecot listening on the network (port 24/tcp)
> for incoming mail. No need for postfix on the backend mailstorage
> servers.
> 
> Our setups has been:
> 
>     Mailgw[1-14] ---smtp-->  dovecot-server[1-5] (postfix + dovecot/lda)
> 
> and used MX priorities to make all deliveries go to the same
> dovecot-server with the others as backup.
> 
>     $ dig mx deliver.example.com +short
>     10 dove2.example.com.
>     15 dove3.example.com.
>     20 dove4.example.com.
>     25 dove5.example.com.
>     5 dove1.example.com.
> 
> 
> Now I'm moving towards:
> 
>     Mailgw[1-14] ---lmtp-->  dovecot-server[1-5] (dovecot/lmtp)
> 
> but worry that the index corruption might hit me again.. Ideally
> I want:
> 
>     Mailgw[1-14] ---lmtp-->  directors --lmtp-->  dovecot-server[1-5] (dovecot/lmtp)
> 
> but lmtp-proxying seems to have bugs (ref: my latest mails to this
> list).
> 
> 
>    -jf