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Re: mail servers + ldap load balancing



--On Tuesday, August 10, 2004 2:10 PM -0400 James Courtney <Jcourtney@inphonic.com> wrote:

We have an environment with several mail servers (currently 3) each
running various SMTP, POP, and IMAP.  The software utilized is Postfix
(with Courier maildrop) and Courier pop3d and imapd.  All of these
authenticate against our OpenLDAP server(s).  We are entertaining a
couple of replication/loadbalancing scenareos:

For both scenareos place the master LDAP server on a dedicated machine.

- Scenareo I -

Each mail server has it's own replicated instance of OpenLDAP running and
references it using localhost for minumum network latency/utilization.


- Scenareo II -

We maintain a cluster or repliated OpenLDAP instances (possibly running
on each mail server) and these are IP load balanced and referenced
through a single domain name.



Which of these if preferable? Should we consider something different?

I'd say II is preferable, because then load generated by the mail delivery system does not effect the response time of the directory service. Scenario II is essentially what Stanford does (we have 3 email routing systems that query 3 load-balanced OpenLDAP servers).

With today's high level of spam and virus related traffic, the sudden floods of email against a shared set of servers could have a particularly adverse affect.

You might find:

<http://tools.stanford.edu/cricket?target=/ldap>

interesting. I suggest looking at the "binds-mail" and "searches-mail" categories. These two sections document the connections from our email routers to our email dedicated directory servers.

--Quanah

--
Quanah Gibson-Mount
Principal Software Developer
ITSS/Shared Services
Stanford University
GnuPG Public Key: http://www.stanford.edu/~quanah/pgp.html