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Subject: Re: pop-before-smtp (was Re: FreeInet and checking mail?)
From: Brad Knowles (blkskynet.be)
Date: Wed Jun 07 2000 - 19:18:41 CDT

At 10:44 PM +0300 2000/6/7, Yiorgos Adamopoulos wrote:

> So what happens if this server fails? Do you get 600K telephone calls at
> the helpdesk?

        This server very, very rarely fails. We've been very careful in
designing it that way. However, this is just one building block in
the scalable mail system we're designing -- we're shooting for tens
of millions of users, and we don't want to have to try to manage
hundreds of thousands of servers to do that. We'd be much happier
managing just a couple dozen.

> - You can afford to have 600K users spread to 10 machines of 60K users
> each (and something along the lines the www.mirapoint.com solution
> proposes).

        Doesn't scale to tens of millions of users.

> - Your solution cannot scale. And it cannot scale not because it supports
> 600K users, but because at the first HW failure everyone loses service.

        We don't have all that many users today, but we see what is
rapidly coming down the pike, and in just a couple of years, I fully
expect us to literally have tens of millions of users. Trying to put
together a system to handle tens of millions of users where each
building block can only handle a few thousand just won't work.

        Our solution is relatively brittle today, because we have a
smaller number of servers relative to the size of our customer base,
but the MTBF on this hardware has so far proven to be pretty good,
and we think we're striking a good balance between the two paradigms
of the ultra low-end "one box per user and no one notices if it dies"
and the ultra high-end "one box for all users, and the Universe
should end before the computer system does".

> Yes, having IMAP means taking up more resources, but this is not necesarily
> bad. It depends on what you want to do with it and what you want your users
> to do with it.

        No, I pretty much consider this to be necessarily bad. Being
able to handle certain additional features is nice, but when I have
to throw ten or a hundred times as much hardware at the problem to
have those additional features, well it just makes me want to puke. 

--
   These are my opinions -- not to be taken as official Skynet policy
======================================================================
Brad Knowles, <blkskynet.be>                || Belgacom Skynet SA/NV
Systems Architect, Mail/News/FTP/Proxy Admin || Rue Colonel Bourg, 124
Phone/Fax: +32-2-706.13.11/12.49             || B-1140 Brussels
http://www.skynet.be                         || Belgium