SLUG Mailing List Archives
Re: [SLUG] Opinions sought: Exim vs Sendmail
- To: "Jeff Waugh" <jdub@xxxxxxxxxxxxxx>
- Subject: Re: [SLUG] Opinions sought: Exim vs Sendmail
- From: "Oscar Plameras" <oscarp@xxxxxxxxxxx>
- Date: Tue, 24 Jun 2003 22:47:32 +1000
- Cc: slug@xxxxxxxxxxx
- Cc: James_Gray@xxxxxxx
From: "Jeff Waugh" <jdub@xxxxxxxxxxxxxx>
> On Tue, 2003-06-24 at 04:04, Oscar Plameras wrote:
> > It is also a good idea to take the /usr/local/sbin/named
> > away to another FreeBSD/Linux box. DNS lookups is
> > always a slow process and queues other processes
> > particularly during Internet peak hours.
> > Because the box is mainly Email services, and not
> > transaction type application such as financial databases, it
> > will help alleviate processing bottle neck by increasing
> > the time between disc sync'ing as done by the (syncer)
> > process.
> It wouldn't be a good idea to shift DNS away from the email server -
> much of what an MTA does is DNS lookups, so it is always a good idea to
> have a fast, caching name server on the local machine. Better throughput
> through better latency.
> Caching (or authoritative, for that matter, on an unbusy domain) DNS
> isn't a horribly expensive process.
True, email services is dns service intensive. It demands both forward and
reverse lookup services. So, when MTA requires DNS services it is
serviced by named in the same box. First, the catch is, named is less
in this particular box with 0.0/1.6 percent CPU utilisation. Sustained CPU
activity is more important for the main task done by spamd as indicated by
78.1/14.7 percent CPU/MEM utilisation. The fact that named has far less
activity in this box is perhaps due to spamd being so aggressive and leaves
little time for other processes to spawn when it should. By moving it to
another box within the same network may make both named and spamd
happier and livelier.
Secondly, with named servicing the MTA in the box, it also answers
service request from other services outside this particular box. It is
that time that the DNS in this MTA box spends servicing others
that we do not wish to loss in view of the capacity requirements
for CPU utilisation by spamd. The advantage of named being in the
same box as the MTA is negated and lossing more.
It sounds to me like this network is rather busy with a number of
domains and users being served. 60Gb of email data in a day alone
tells the story.