[Mimedefang] Off Topic - Mail Message and MySQL

David F. Skoll dfs at roaringpenguin.com
Wed Jun 18 13:23:01 EDT 2003


On Wed, 18 Jun 2003, Phil Eschallier wrote:

> I believe that I could have expressed my thoughts better.  Actually, I was
> thinking that "what if the DB server is down or you hit your connect limit?"

In our case, it's optional as to whether you tempfail the mail or just deliver
it unscanned.

> A flood of spam or virus traffic could easily
> push connections up to a high level

The number of connections is bounded by the maximum number of slaves.  It's
one DB connection per slave only.

> In contrast, the file system should always be there (I'll probably receive a
> shot or two for that statement).

A flood of spam can use up all your I/O bandwidth, whether the I/O is
on your disk controller or to the database.  It's not clear to me that
the database would be swamped before the disk is swamped, especially
if you run the DB on the same machine as MIMEDefang (the typical
situation for our customers.)  The DB really is just another type of
file system.

There might even be an argument that a DB with write-ahead log files
might make better use of disk I/O than putting lots of small files in
lots of different disk directories.  A single disk seek costs way more
than a bunch of writes in nearby disk locations.

This is all theoretical, of course!  I haven't run measurements comparing
the approaches. :-)

--
David.





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