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Subject: Re: SCSI, U2W in particular?, and poor performance...
From: Wietse Venema (wietseporcupine.org)
Date: Sun Mar 05 2000 - 17:17:05 CST

Rich Graves:
> Justin Robertson said:
> >
> > Prehaps you'd like to tell me why sendmail outperformed postfix on the
> > SCSI machine then? hmm?
>
> We don't know for sure what your syncing behavior is, but regardless the
> default monolithic sendmail installation does less disk I/O than postfix.

Where's the difference? Sendmail tries to deliver by default, which
involves a half-dozen of files.

In queue-only mode, sendmail manipulates the following files, according
to the strace command:

    create qf<QUEUE ID>
    create xf<QUEUE ID>
    create df<QUEUE ID>
    create tf<QUEUE ID>
    rename tf<QUEUE ID> to qf<QUEUE ID>
    remove xf<QUEUE ID>

That's Sendmail 8.9.3, invoked with -O DeliveryMode=queue.

Postfix is optimized for receiving mail via SMTP:

    create incoming/temporary-name
    rename incoming/temporary-name to incoming/<QUEUE ID>

With local submission, mail is copied by a privileged process in
order to cross the boundary between user-land and Postfix:

    user-land:
        create maildrop/temporary-name
        rename maildrop/temporary-name to maildrop/<QUEUE ID>

    pickup/cleanup daemon:
        open maildrop/<QUEUE ID>
        create incoming/temporary-name
        rename incoming/temporary-name to incoming/<NEW QUEUE ID>

> To get sendmail to behave like the default postfix installation you'd set
> in sendmail.cf
>
> # default delivery mode
> O DeliveryMode=queue
> # queue up everything before forking?
> O SuperSafe=True
>
> A high-volume production sendmail installation would probably set these
> anyway.

        Wietse