Author: W B Hacker Date: To: exim users Subject: Re: [exim] changing mailstores
Graeme Fowler wrote: > On Wed, 2012-10-03 at 13:02 +0100, paul.osborne@??? wrote:
>> As part of the process I intend to shutdown SMTP on mailstoreA in order
>> to force mail to queue on my Exim routing host - this I am happy with.
>
> OK, but...
>
>> However changing the mailstore requires changing the routing data in the
>> underlying database used by Exim so address xyz@??? routes to
>> mailstoreB - again updating the underlying database is something I am
>> happy with.
>
> Excuse me going *yick* at this idea :)
>
> If it was me doing this, I'd:
>
> 1. bring up B alongside A
> 2. force A to not deliver locally but smarthost to B
> 3. change global routing data to route to B
>
> That way you have a transparent changeover without having to take
> anything down until you're sure all the mail has drained from A and all
> other mail is going to B; then you can shutdown A.
>
> Of course... if A is a closed box with no knobs you can turn to achieve
> this, the idea won't float.
>
> Graeme
>
> Seconding Graeme's concept (we've done it in a similar way, and more
than once), and yes it probably CAN float even if all that can be
reached is Exim's config file.
Besides abrupt repointing in the routers, consider also slotting in an
'unseen' that duplicates delivery for a period of parallel-cutover time.
Best proof you can have that nothing is being lost is a comparison
between turn-up timestamp and t+(n) that finds both mailstores match.
