Re: [exim] overall rate limiting?

On Tue, May 23, 2006 at 03:32:03PM +0200, H. Wilmer wrote:
> Peter D. Gray wrote:
>
> > as well. It would be nice to set up the
> > routing machines so that they process a fixed number of
> > email messages per second. This would avoid large load spikes
> > on our mail stores as mail floods in.
> >
> > Any ideas or suggestions?
>
> To even out the load, you can try tweaking these options:
>
>
> deliver_queue_load_max = 2.00
> queue_only_load = 1.50
> remote_max_parallel = 16
>

Rememeber it is my mail stores I am trying to protect
from the mail floods.

The above will help the hubs, but may make things worse for the
stores, since the queue will be processed in a batch.

>
> It's probably much better than limiting to handling x mails per unit of
> time because it allows the servers to operate at full throttle without
> being overwhelmed by the amount of mail to handle, provided that you use
> reasonable values adapted to the performance of your servers. If that
> doesn't suffice, you will need faster or more servers anyway.
>

As I say, by solaris mail hubs are not the problem.
But when the mail gets to the stores, they kind of
get slow. It would be nice if the smtp system on the
mail stores knew its own limits and only accepted
email at a rate it can handle, but that is not the case.

In some sense this is a DOS defence as well.
No matter how much machinery I throw at the hubs
or the stores, I suspect I can always have performance
problems with high enough email rates.

I am routinely seeing mail rates of 60 per second
for minutes at a time now, mainly spam.

Regards,
pdg

--

See mail headers for contact information.