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From: spambox on 7 May 2010 08:38
Hello everyone.

This is my first question here so please forgive me if i'm out of topic or something...


I'm building up this architecture with postfix + ldap + Courier IMAP
(i hope the below ascii art is displaying correctly :)



|-------------|
| postfix1 | very big storage
| LDAP1 |-------------|********************
| server1 | | *
|-------------| | /home1 *
| | *
| |-------------------*
|-------------| | *
| postfix2 | | *
| LDAP2 |-------------| /home2 *
| server2 | | *
|-------------| | *
| |-------------------*
| | *
|-------------| | /home3 *
| postfix3 | | *
| LDAP3 |-------------|********************
| server3 |
|-------------|




Now, let me explain how this is going to work.
This architecture works with Qmail+Ldap, i need to use PostFix instead (for many reason)

server1,2,3 have 1 balancer in fron which simply redistribute the traffinc among the 3 servers.

if one server goes down, the one next to him will Up his ip address and mount his partition on the storage untill the server restarts correctly.

Now, i've a couple of questione here.


1) I've never used Courier IMAP, but reading on the internet i've found that it use gethostbyname() to resolve and this may cause an infinite loop for a host with 2 interface but one hostname if one server goes down.
So, i'm afraid that i will be able to installa courier-imap on each server and this will cause a big problem to the scalability of the system.

2) Has anyone ever tryed something like this and its ablet to redirect me to some good documentation?


Thank you very much for your time and for any tip or advice.

Good bye everyone.




--
spambox <spambox(a)fastwebnet.it>

From: mouss on 7 May 2010 17:48
spambox a �crit :
> Hello everyone.
>
> This is my first question here so please forgive me if i'm out of topic or something...
>
>
> I'm building up this architecture with postfix + ldap + Courier IMAP
> (i hope the below ascii art is displaying correctly :)
>
>
>
> |-------------|
> | postfix1 | very big storage
> | LDAP1 |-------------|********************
> | server1 | | *
> |-------------| | /home1 *
> | | *
> | |-------------------*
> |-------------| | *
> | postfix2 | | *
> | LDAP2 |-------------| /home2 *
> | server2 | | *
> |-------------| | *
> | |-------------------*
> | | *
> |-------------| | /home3 *
> | postfix3 | | *
> | LDAP3 |-------------|********************
> | server3 |
> |-------------|
>
>
>
>
> Now, let me explain how this is going to work.
> This architecture works with Qmail+Ldap, i need to use PostFix instead (for many reason)
>
> server1,2,3 have 1 balancer in fron which simply redistribute the traffinc among the 3 servers.
>
> if one server goes down, the one next to him will Up his ip address and mount his partition on the storage untill the server restarts correctly.
>
> Now, i've a couple of questione here.
>
>
> 1) I've never used Courier IMAP, but reading on the internet i've found that it use gethostbyname() to resolve and this may cause an infinite loop for a host with 2 interface but one hostname if one server goes down.
> So, i'm afraid that i will be able to installa courier-imap on each server and this will cause a big problem to the scalability of the system.
>
> 2) Has anyone ever tryed something like this and its ablet to redirect me to some good documentation?
>

courier has its own mailing lists where you'll get better support. I
doubt you'd have any problem here but you'd better ask courier experts
on courier lists.

note that email encompasses two completely different things:
- mail transport which postfix does well.
- mail retrieval (pop3, imap, webmail). this is a different thing and is
out of topic here.

>
> Thank you very much for your time and for any tip or advice.
>
> Good bye everyone.
>
>
>
>

From: Jose Ildefonso Camargo Tolosa on 10 May 2010 01:30
Hi!

Yes, I know, this is kinda off-topic, but looks interesting.

On Fri, May 7, 2010 at 8:08 AM, spambox <spambox(a)fastwebnet.it> wrote:
> Hello everyone.
>
> This is my first question here so please forgive me if i'm out of topic or something...
>
>
> I'm building up this architecture with postfix + ldap + Courier IMAP
> (i hope the below ascii art is displaying correctly :)

A little messy, I would need to see it on a monospace font, I guess.

>
>
>
> |-------------|
> |   postfix1  |               very big storage
> |   LDAP1     |-------------|********************
> |   server1   |             |                   *
> |-------------|             |   /home1          *
>       |                    |                   *
>       |                    |-------------------*
> |-------------|             |                   *
> |   postfix2  |             |                   *
> |   LDAP2     |-------------|   /home2          *
> |   server2   |             |                   *
> |-------------|             |                   *
>       |                    |-------------------*
>       |                    |                   *
> |-------------|             |   /home3          *
> |   postfix3  |             |                   *
> |   LDAP3     |-------------|********************
> |   server3   |
> |-------------|
>
>
>
>
> Now, let me explain how this is going to work.
> This architecture works with Qmail+Ldap, i need to use PostFix instead (for many reason)
>
> server1,2,3 have 1 balancer in fron which simply redistribute the traffinc among the 3 servers.

Ok, so, load balancing here, with different homes for each server, so,
each server have its own "set of users", right?

>
> if one server goes down, the one next to him will Up his ip address and mount his partition on the storage untill the server restarts correctly.

Now, this is more typical of HA clusters, what gets me confused is
what I asked on the last question, so, when say, server 1 goes down,
server 2 mount server1's home partition and start getting mails (and
serving IMAP requests) as if it were server1, right? I'll reserve my
other comments until I get more information on this.

>
> Now, i've a couple of questione here.
>
>
> 1) I've never used Courier IMAP, but reading on the internet i've found that it use gethostbyname() to resolve and this may cause an infinite loop for a host with 2 interface but one hostname if one server goes down.
> So, i'm afraid that i will be able to installa courier-imap on each server and this will cause a big problem to the scalability of the system.
>
> 2) Has anyone ever tryed something like this and its ablet to redirect me to some good documentation?

I don't use Courier (several reasons, off-topic here), I use Dovecot
(I can even use SASL from Dovecot to authenticate Postifx's smtp,
really handy along with reject_authenticated_sender_login_mismatch and
smtpd_sender_login_maps on ldap).

>
>
> Thank you very much for your time and for any tip or advice.
>
> Good bye everyone.
>
>
>
>
> --
> spambox <spambox(a)fastwebnet.it>
>

From: spambox on 10 May 2010 07:17


On Mon, 10 May 2010 01:00:29 -0430
Jose Ildefonso Camargo Tolosa <ildefonso.camargo(a)gmail.com> wrote:

> Hi!
>
> Yes, I know, this is kinda off-topic, but looks interesting.

Thank you for your interest!

> > |-------------|
> > |   postfix1  |               very big storage
> > |   LDAP1     |-------------|********************
> > |   server1   |             |                   *
> > |-------------|             |   /home1          *
> >       |                    |                   *
> >       |                    |-------------------*
> > |-------------|             |                   *
> > |   postfix2  |             |                   *
> > |   LDAP2     |-------------|   /home2          *
> > |   server2   |             |                   *
> > |-------------|             |                   *
> >       |                     |-------------------*
> >       |                    |                   *
> > |-------------|             |   /home3          *
> > |   postfix3  |             |                   *
> > |   LDAP3     |-------------|********************
> > |   server3   |
> > |-------------|
> >
> >
> >
> >

> Ok, so, load balancing here, with different homes for each server, so,
> each server have its own "set of users", right?

Yes, each LDAP have list of his users. For each LDAP entry we have a record telling us, who is the Mail server for that user. So if the balancer send user "test" to mail server1 and from the LDAP we see that "test" user belong to server1 then "test" request is served, ELSE if user "test" has mail server set on "mailserver3" for example, the request is redirect to mailserver3 that will handle his request.


> >
> > if one server goes down, the one next to him will Up his ip address and mount his partition on the storage untill the server restarts correctly.
>
> Now, this is more typical of HA clusters, what gets me confused is
> what I asked on the last question, so, when say, server 1 goes down,
> server 2 mount server1's home partition and start getting mails (and
> serving IMAP requests) as if it were server1, right? I'll reserve my
> other comments until I get more information on this.

Yes, if server1 goes down the cluster will mount up server1 interface and home partition on server2. Server2 will temporarily act as server1 and server2 untill server1 is back on line.




> > 1) I've never used Courier IMAP, but reading on the internet i've found that it use gethostbyname() to resolve and this may cause an infinite loop for a host with 2 interface but one hostname if one server goes down.
> > So, i'm afraid that i will be able to installa courier-imap on each server and this will cause a big problem to the scalability of the system.
> >
> > 2) Has anyone ever tryed something like this and its ablet to redirect me to some good documentation?
>
> I don't use Courier (several reasons, off-topic here), I use Dovecot
> (I can even use SASL from Dovecot to authenticate Postifx's smtp,
> really handy along with reject_authenticated_sender_login_mismatch and
> smtpd_sender_login_maps on ldap).

Nice, i gave a look to this Dovecot and its looks pretty nice! i'vent tested it yet but it seems it can be a valid alternative. Im trying to move from Qmail to postfix because Qmail is patch-project(dead), while i think Postfix is a valid alternative that will make life a lot easyer.




--
spambox <spambox(a)fastwebnet.it>

From: Jose Ildefonso Camargo Tolosa on 10 May 2010 17:53
Hi!

On Mon, May 10, 2010 at 6:47 AM, spambox <spambox(a)fastwebnet.it> wrote:
>
>
> On Mon, 10 May 2010 01:00:29 -0430
> Jose Ildefonso Camargo Tolosa <ildefonso.camargo(a)gmail.com> wrote:
>
>> Hi!
>>
>> Yes, I know, this is kinda off-topic, but looks interesting.
>
> Thank you for your interest!
>
>> > |-------------|
>> > |   postfix1  |               very big storage
>> > |   LDAP1     |-------------|********************
>> > |   server1   |             |                   *
>> > |-------------|             |   /home1          *
>> >       |                     |                   *
>> >       |                     |-------------------*
>> > |-------------|             |                   *
>> > |   postfix2  |             |                   *
>> > |   LDAP2     |-------------|   /home2          *
>> > |   server2   |             |                   *
>> > |-------------|             |                   *
>> >       |                     |-------------------*
>> >       |                     |                   *
>> > |-------------|             |   /home3          *
>> > |   postfix3  |             |                   *
>> > |   LDAP3     |-------------|********************
>> > |   server3   |
>> > |-------------|
>> >
>> >
>> >
>> >
>
>> Ok, so, load balancing here, with different homes for each server, so,
>> each server have its own "set of users", right?
>
> Yes, each LDAP have list of his users. For each LDAP entry we have a record telling us, who is the Mail server for that user. So if the balancer send user "test" to mail server1 and from the LDAP we see that "test" user belong to server1 then "test" request is served, ELSE if user "test" has mail server set on "mailserver3" for example, the request is redirect to mailserver3 that will handle his request.

Cool, I have implemented a similar approach, but on postfix level, ie,
each smtp server can receive mail for any user, and then look for the
smtp server on a ldap attribute (I use maildrop attr for that). I use
this to have a "distributed email system", so that each user have its
mail "locally" on the locality he/she works. If one server is
unavailable, the system will keep the mail queued until the
corresponding server is back, so: no HA here.

>
>
>> >
>> > if one server goes down, the one next to him will Up his ip address and mount his partition on the storage untill the server restarts correctly.
>>
>> Now, this is more typical of HA clusters, what gets me confused is
>> what I asked on the last question, so, when say, server 1 goes down,
>> server 2 mount server1's home partition and start getting mails (and
>> serving IMAP requests) as if it were server1, right? I'll reserve my
>> other comments until I get more information on this.
>
> Yes, if server1 goes down the cluster will mount up server1 interface and home partition on server2. Server2 will temporarily act as server1 and server2 untill server1 is back on line.

Ok.

>
>
>
>
>> > 1) I've never used Courier IMAP, but reading on the internet i've found that it use gethostbyname() to resolve and this may cause an infinite loop for a host with 2 interface but one hostname if one server goes down.
>> > So, i'm afraid that i will be able to installa courier-imap on each server and this will cause a big problem to the scalability of the system.
>> >
>> > 2) Has anyone ever tryed something like this and its ablet to redirect me to some good documentation?
>>
>> I don't use Courier (several reasons, off-topic here), I use Dovecot
>> (I can even use SASL from Dovecot to authenticate Postifx's smtp,
>> really handy along with reject_authenticated_sender_login_mismatch and
>> smtpd_sender_login_maps on ldap).
>
> Nice, i gave a look to this Dovecot and its looks pretty nice! i'vent tested it yet but it seems it can be a valid alternative. Im trying to move from Qmail to postfix because Qmail is patch-project(dead), while i think Postfix is a valid alternative that will make life a lot easyer.

postfix is extremely flexible. Believe me: you can replace qmail with
*no* changes to your ldap entries.

Your project looks interesting,

Ildefonso Camargo

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