On Thu, Dec 03, 1998 at 11:00:03AM -0000, michael@??? wrote:
> I thought about using OS quota, but I really do not want to create a UNIX
> user for each POP3 user, so I use exim quotas. I already found out that
> using Maildir, delivery gets very slow as the number of emails increases,
> because exim stats all files to calculate the mail box size. I guess that's
> something we have to live with. SMP machines will help to provide more CPU
> power per machine.
You don't neccessarily have to create a new user to implement this in the OS.
There are ways to impose quotas on directory structures rather than by user, if
you are using the maildir format you apply these to the top level directory of
the users maildrop. The advantage gained is to leverage the performance increase
in not having to calulate mailbox sizes (through exim).
Maildir delivery is slightly higher in processing requirements but this is offset
by a greater increase in POP retrvial. It also eliminates a lot of locking issues.
The price in terms of processing ticks is well worth this.
> >
> > About 102,000 requests per day for a user base of 40,000 customers.
>
> Only 2.55 requests per day for each customer? That's good news.
In the ISP world you will find that a siginfigant number of mail users will
retrieve their mail <= once a week.
>
> To me, that means: Indeed, not even 3 million emails per day, assuming
> an even load distribution over time. Unfortunately, that assumption
> does not hold and I don't want to have other systems retry often until
> they finally get through during rush hours. I will use DNS RR sets for a
> scalable input queue, but I still would like a higher rate for incoming
> mail, because it would save hardware. I certainly hope that exim only
> forks a process per email instead of using fork()/exec()?
>
Assuming that your total incoming SMTP transactions are at 3 million per day then you
need something other than RR DNS to ensure that you have an SMTP service available
100% of the time. Dist Director, Fake or some other clustering/failover solution
would be needed.
Conor.
--
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Conor Mc Goveran, conor@???
Systems Operator,
Telecom Internet http://www.tinet.ie
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