Quoth Pedro Crespo on Wed, Apr 11, 2001:
> OK, that mean if you want to increase your mail system size, you add more computers (horizontal growth) better
> than to add more CPU's in a single computer (vertical growth).
Adding more computers is good for high availability and (if your
installation is big) increasing filesystem throughput. But, as
it was said before and I will say it again, CPU is definitely not
a problem, and Exim will gain no advantage *whatsoever* from
multithreading (this is the reason it's not multithreaded, not
POSIX or whatever else). It forks and changes UIDs, so
multiprocessing (miltiple processes, not multiple processors)
does make lots of sence (in fact, every other mailer daemon on
UNIX forks, and not one of them is multithreaded, for precisely
the same reasons).
Adding more memory can be great. Using a fast filesystem[0] is
also very neat. It all boils down to the size of your
installation. If you have a couple of dozens thousands of users,
you probably don't need all that. If you have a really big ISP,
you need to think of that.
Vadik.
[0] BSD FFS with soft updates enabled is the best for this
purpose, log filesystem is not bad either. And, of course,
the faster the disks are the better. This is for local
spool; for mailboxes themselves, if you use several
computers, get a NetApp or something.
--
Spelling is a lossed art.
