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292438Re: R: Scheduling policies for outgoing smtp server

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  • Wietse Venema
    Apr 8 4:47 PM
      Simone Caruso:
      > On 06/04/2013 15:01, Wietse Venema wrote
      > > There must be other solutions that can work with a fixed memory
      > > budget and that can push excessive mail to a "low-priority" queue
      > > that is processed when it does not interfere with other delivery.
      > >
      > > Any solution that requires knowledge of THE COMPLETE MAIL QUEUE
      > > will be firmly rejected. I will not allow a built-in limitation on
      > > the amount of mail that Postfix can handle.
      > >
      > (if i understood correctly the needs of Giorgio)
      > Can be the following points the way to obtain round-robin delivery based on
      > sender address/ip?
      >
      > 1. change the "incoming queue" directory structure indexing sub-directories with
      > a per-sender index
      > 2. changing the algorithm used by qmgr to move email from "Incoming" to "Active"
      > queue, (a foreach over subdirs)
      >
      > This increases disks i/o but you can obtain a pretty fair delivery
      > between senders

      I just simulated the performance hit of 256 incoming queues by setting

      hash_queue_names = incoming
      hash_queue_depth = 2

      and running smtp-source, sending mail to an alias for /dev/null.

      Postfix queue performance for small messages already dropped by
      30%, with the write cache enabled on a 10,000RPM SAS disk (which
      is recommended for a production server only when the write cache
      has a battery to survive power failures).

      The performance drop will be worse with one queue directory per
      customer, unless you have very few customers of course.

      Wietse
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