MS performance as a gateway comments

Martin Hepworth martinh at SOLID-STATE-LOGIC.COM
Fri Nov 5 17:31:51 GMT 2004


your specs and message flow don't seem to match the other high end boxes
(ie you system should be able to handle well over a million messages aday).

what extra SA rules are you running? I wonder if some of the larger ones
are causing problems (not to mention the RBLs - are you running a local
caching nameserver on t he box0?

Martin Hepworth
Snr Systems Administrator
Solid State Logic
Tel: +44 (0)1865 842300

Alan wrote:
> This is just some of the things I have experienced over the last year
> related to performance. FWIW, maybe it will help someone down the line...
> I have been running MS/SA for about a year now, and have been struggling
> with performance issues since day one. Over this time, many of you have
> greatly helped me in my tweaking, including:
> tempfs for working dir
> seperate scsi drive for queue partition
> reiserfs for queue fs
> dual pent 4 with 2 gig ram
> minimal logging
> smaller batch size (20)
> In my configuration, I have 4 smtp servers receiving email from the outside
> world. Each of these 4 servers route the mail they accept directly to my
> MS/SA server for spam/virus/exploit filtering. Everything that is passed by
> MS/SA is then finally sent on to a final smtp server where the inboxes
> reside. So you can see that my MS/SA server acts as a gateway; it accepts
> no email directly from the outside world, and it has no inboxes on it.
> About 300,000 emails per day enter the MS/SA server, and its filtering out
> about 72% of that volume, passing the rest on to my users.
> In my original install, I was using sendmail as the MTA. During much of the
> day, so many MTAs were running that server load would hover around 14-20.
> During quieter times, it would drop to maybe 5-7, never below. If I
> configured sendmail to limit MTAs, I would have backups on the 4 incoming
> smtp servers as they could not deliver their queues to the MS/SA server
> fast enough, and/or there would be backups in the delivery queue of the
> MS/SA server itself as there were not enough MTAs available for final
> delivery to the inbox server. If I ran enough MTAs to handle incoming and
> outgoing traffic, load would be so high that MS became the bottle neck.
> Bayes tests were out of the question due to load, and various network tests
> (razor2, surbl etc.) often had to be disabled when back logs were bad. It
> was not uncommon each day to have 20,000 messages waiting to be processed.
> During daily heavy load, the time from when an email hit my first server
> until it was dropped into the user's inbox would be 4-7 hours.
> A couple of months ago I replaced sendmail as the MTA with exim. I really
> liked exim's configuration flexability and features, and was quickly able
> to get some neat tweaks running. I found that each exim MTA seemed to use
> less resources than each sendmail MTA had used, and I was able to keep
> network tests running much more often. It was an improvement, but loads
> were still usually above 8 and total delivery time was still poor,
> sometimes as high as 2 hours during the day.
> Now I have replaced exim with zmailer, and all I can say is WOW! First,
> zmailer reuses the same tcp/ip connection to my final inbox server for as
> long as there are messages in the delivery queue to be delivered. This
> means there is never more than a single MTA running to deliver messages.
> Secondly, the zmailer smtpserver process that receives incoming messages
> from my 4 smtp servers, along with the zmailer smtp process that delivers
> filtered messages to my inbox server all use minimal system resources.
> Since switching to zmailer as my MTA, system load is averaging under 4, and
> very few peaks above 5, and they are very short. Pre-filtered queue size
> has yet to go over 100 during peak hours, as opposed to previous queue
> sizes of over 10,000. Delivery queue size is likewise low, typically under
> 50. Delivery time from initial reception to user inbox is now down to 3
> minutes or so.
> So, if you are struggling with system load and bottlenecks as I have been,
> and have made all the hardware tweaks you can think of, I HIGHLY recommend
> you try zmailer as your MTA.
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