[Mailman-Developers] VERPing: ouch!

[Nigel Metheringham]

On Tue, 2004-07-13 at 12:52, Brad Knowles wrote:
> At 11:08 AM +0200 2004-07-13, Fil wrote:
> >  I hope this feedback can be useful, if you have scalability in mind for MM3.
> 
> 	This is really more of an MTA limitation, although there might be 
> some things we can do to try to work around it with Mailman.  For 
> example, it might be faster/lower overall load on the server if we 
> had the MTA do the VERPing for us -- we're pretty sure that's 
> supported by some MTAs (e.g., at least some versions of Exim), and we 
> know it's faster for at least some of them (e.g., Exim).

If you are doing VERP in MM then you send one message per recipient from
MM to your MTA.  Thats the think that will cause problems on many
systems because you will need almost as much spool space as the message
multiplied by the recipient count (almost as much because some of the
early messages will have left the box by the time the last ones come
in).

I guess that the awful performance in this case is probably down to
something like the MTA doing verification on sender/recipient inline,
which will slaughter performance.

We are very very shortly going to convert exim.org to a new platform
with new Mailman installation, which I intend to do VERP deliveries on. 
I can use that box, when in use, to test VERP on MM against VERP within
exim, and I'll write up my results.  However I am looking at 2K users -
not 150K, and it maybe that there are scaling problem

As a blatant and unwarranted plug, the Exim/Mailman HOWTO gives
information on using VERP with Exim
	http://www.exim.org/howto/mailman21.html

Cheers
	Nigel.

[At an exim conference :-) ]

-- 
[ Nigel Metheringham           Nigel.Metheringham at InTechnology.co.uk ]
[ - Comments in this message are my own and not ITO opinion/policy - ]