On Tue, 10 Dec 1996, Paul Graham wrote:
> despite the assessment implied by ``Blech'' qmail is trivially an order
> of magnitude faster than sendmail. i used to use sendmail on our list
a "trivial order of magnitude" or "trivially an order of magnitude"? :)
the qmail page describes performace differences as follows. But some of
these seem based on the same tests denounced as "not real world" in
earlier threads, i.e. on a LAN, etc.??
Scheduling: I sent a message to 8192 ``trash'' recipients on my home
machine. All the deliveries were done in a mere
78 seconds---a rate of over 9 million deliveries a day! Compare this
to the speed advertised for Zmailer's scheduling:
1.1 million deliveries a day on a SparcStation-10/50. (My home
machine is a 16MB Pentium-100 under BSD/OS, with
the default qmail configuration. qmail's logs were piped through
accustamp and written to disk as usual.)
Local mailing lists: When qmail is delivering a message to a
mailbox, it physically writes the message to disk before it
announces success---that way, mail doesn't get lost if the power
goes out. I tried sending a message to 1024 local
mailboxes on the same disk on my home machine; all the deliveries
were done in 25.5 seconds. That's more than 3.4
million deliveries a day! Sending 1024 copies to a single mailbox
was just as fast. Compare these figures to Zmailer's
advertised rate for throwing recipients away without even delivering
the message---only 0.48 million per day on the
SparcStation.
Mailing lists with remote recipients: qmail uses the same delivery
strategy that makes LSOFT's LSMTP so fast for
outgoing mailing lists---you choose how many parallel SMTP
connections you want to run, and qmail runs exactly that
many. Of course, performance varies depending on how far away your
recipients are. The advantage of qmail over
other packages is its smallness: for example, one Linux user is
running 60 simultaneous connections, without swapping,
on a machine with just 16MB of memory!
Separate local messages: What LSOFT doesn't tell you about LSMTP is
how many separate messages it can
handle in a day. Does it get bogged down as the queue fills up? On
my home machine, I disabled qmail's deliveries and
then sent 5000 separate messages to one recipient. The messages were
all safely written to the queue disk in 23
minutes, with no slowdown as the queue filled up. After I reenabled
deliveries, all the messages were delivered to the
recipient's mailbox in under 12 minutes. End-to-end rate: more than
200000 individual messages a day!
Overall performance: What really matters is how well qmail performs
with your mail load. Red Hat Software found
one day that their mail hub, a 48MB Pentium running sendmail 8.7,
was running out of steam at 70000 messages a day.
They shifted the load to qmail---on a smaller machine, a 16MB
486/66---and now they're doing fine.
Follow-Ups:
References:
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