On Tue, 2008-08-26 at 07:04 -0400, Sam Varshavchik wrote:
> Svetozar Mihailov writes:
> 
> > Hello all,
> > 
> > I'm building Courier Cluster and have few questions.
> > 
> > Hardware details:
> > 4 core quad servers with 8GB ram, iscsi storage with gfs2. Full cluster
> > will have total 8 servers.
> > 
> > Questions:
> > 
> > 1. Sam, This cluster will offer free hosting ( mail and www ) services
> > for our customers which already pay for internet connectivity. Do I need
> > some kind of license for courier suite? Is this changes if this hosting
> > also offer payed services?
> 
> No and no.
> 
> > 2. DNS: Which dns structure is allowed/better:
> > 
> > 2.1 One MX record for mail.example.com and 8 A records for each server.
> > OR
> > 2.2 Eight MX records with equal priority to c(1-8).mail.example.com for
> > smtp and additional eight A records for mail.example.com for pop/imap.
> 
> I would suggest a combination, 4 MX records with two A addresses for each 
> one.
> 
> > 2.2 I do not want to use load balancer because if load balancer dies
> > everything stop. I will implement monitoring (ping?) daemon, which will
> > add/remove servers to dns if some of them dies. Is there recomended
> > minimal TTL for dns records in this case?
> 
> With eight servers, I wouldn't even bother, and leave the default TTL set to 
> one day.
> 
> > 3. Do I need special care of file locking? All servers have consistent
> > view of file system, and is possible one user to login to few servers at
> > same time via pop/imap.
> 
> Locking is used very minimally, only in the IMAP server. No special 
> consideration is necessary.
> 
> > 4. What about MAXPERIP setting? It is possible to make this cluster
> > aware? Otherwise each user can login up to MAXPERIP times on each server
> > at same time.
> 
> No, MAXPERIP is per-server.
> 
> > 5. I think to place /etc/courier and /etc/authdaemon on iscsi/gfs2 so
> > all servers will see same configs all time. Modifying configs and
> > running make* scripts will be done on one separate server. I'm thinking
> > to create additional daemon, which will fam monitor this two folders and
> > issue 'courier restart' and 'service authdaemon restart' on change. Is
> > this will be ok?
> 
> This is ok, but you should carefully set each server's hostname. Each server 
> needs to know its own FQDN.
> 
> > 5.1 /var/spool/courier will be also on iscsi/gfs2, but as I know it is
> > not possible to share this over servers? 
> 
> Correct.
> 
> > 5.2 It is possible at compile time to move certificates
> > from /usr/lib/courier/share to /etc/courier/share? Or just to symlink
> > certificates to /etc/courier/share?
> 
> Use a symlink.
> 
> > 7. I use mysql backed with services separation like this
> > (/etc/courier/imapd):
> > 
> > ADDRESS=0
> > PORT=143,127.0.0.1.144
> > AUTHSERVICE143=imap
> > AUTHSERVICE144=imapl
> > AUTHSERVICE993=imaps
> > 
> > It is possible to setup imap:143 to issue 'imaps' if user send STARTTLS
> > before authentication? Or implement something like AUTHSERVICESSLADD=s'
> > which depends only on connection status (clear/ssl|tls)? Same thing with
> > pop3.
> 
> No, but that's a good point.
> 

Thanks for quick answer. I have few more question which was in first
email blocked because wrong from address ( delete it please ).

5.x Is courier needs write access to /etc/courier
and/or /etc/authdaemon? Is safe to mount them as read-only?

8. I have idea to implement 'ONFAILSQL' and/or 'ONFAILSCRIPT' to
authdaemon. Now I parse maillog file to catch spammers and add them to
local rbl dns server. It will be nice if authdaemon logs directly to
script/sql ip address of failed authentications attempts. Realtime local
blacklist will be very easy with this information. But this will need a
lot of source modification because now authdaemon do now know client ip
address. Similar logging can be implemented in filter to catch positive
spamd/clamd results ( python filter? ).


Best regards,
Svetozar Mihailov



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