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List:       exim-users
Subject:    Re: [Exim] Split mail hub and MX questions
From:       John Horne <J.Horne () plymouth ! ac ! uk>
Date:       2000-08-31 12:19:49
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On 31-Aug-00 at 11:25:48 Mike Meredith wrote:
> On Thu, 31 Aug 2000, John Horne wrote:
>> 1) At present the Uni has one central mailhub with a disaster recovery
>> plan
> 
> We've had two "mail hubs" for some time now --- neither actually holds
> mail (it gets delivered down to NetWare systems plus 1 awkward user who
> insists on his mail being on a Unix system). The "failover" stuff is
> done with MX records, and works sufficiently well that we will take the
> main mail server out of service during working hours for maintenance.
> 
Sounds pretty much like our setup here - no local users as such; all on
Novell servers, w2k servers or 'redirected' to elsewhere (ISP's usually).

> Gotcha's: 
> 
> * An idle backup machine. Our backup machine is quite a capable box,
>   and it may cause problems if people don't understand what it is there
>   for (seeing it as wasted resources).
> 
Hmm, but its not a 'backup' machine as such. In much the same way as the DNS
secondary/slave is 'doing something' all the time.

> * O/s differences. Our mailservers are sufficiently different that we
>   rebuild the data on each box. If you're planning to build the data
>   once, and copy the databases to the other hub, check that this will
>   work.
> 
Yes; but I see no problem here for us.

> Advantages:
> 
> * You can re-build the data on the backup mail server to avoid
>   re-building the data on the main box, and causing problems if the
>   source data is bad (we fetch most of the aliases from the Netware
>   servers which sometimes miss out chunks of the data).
> 
Yes, we too sometimes 'miss out' data from the Novell servers :-( However,
the current software to rebuild the data utilises the last 'good' data for
those servers it misses. Again, this should not be a problem.

>> 2) We used to get ask quite a bit, although not so much now for some
>> reason, the name and/or IP address of the mailhub so that users could
>> configure
> 
> We have a name (smtpserver.port.ac.uk) that is usually two A records
> pointing to both the main mailserver and the backup. When taking the
> main mailserver out, we run a script on the DNS server that changes the
> name to have just one A record. Seems to work quite well.
> 
Ah, yes I see the records (with nslookup). We also dropped the TTL for the
'mail' (your 'smtpserver') records so that anyone caching them would get any
changes quicker than our default 1 day. I think it is set to about 2 hours.
Not sure that's needed, but it shouldn't hurt since I don't think these
records are used that much now.

Thanks for the reply, I seem to be on the right track at least :-)

John.

------------------------------------------------------------------------
John Horne, University of Plymouth, UK           Tel: +44 (0)1752 233914
E-mail: jhorne@plymouth.ac.uk
PGP key available from public key servers

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