[Mimedefang] tmpfs queue directories

Cormack, Ken kcormack at acs.roadway.com
Mon Mar 29 08:38:26 EST 2004


> In that FAQ David recommends 2.5 to 3 times the max message size x the
> maximum number of MD slaves.  Does this still hold true with the newest 
> versions of MD?  That FAQ entry is almost a year old.


Although the recommendatation made in the FAQ has not changed, it might be
helpful to "temper" that recommendation against your actual mail flow.  Your
mileage will definately vary.

For example, on my servers, I track, on a daily basis, such statistics as
average and peak message flow-rates, and average and largest message size.
I also take rapid (every 2-seconds) snapshots of my ramdisk utilization, to
watch for the 24-hour peak.  For example, here are samples from this
morning's reports for one of my systems.  My sendmail allows a max
attachment size of 50MB.

Based on the numbers below, for message flow rates, message volume, and
average message size, I have sized my ramdisk at only 128MB (the O/S rounded
it up to 134MB).  Here's the current df output:

/dev/shm              134MB  4.4MB  129MB   4% /var/spool/MIMEDefang

It has operated that way for several months, with peak utilization seldom
reaching anything close to 70%.  Here are other numbers that support my
decision (and satisfaction with) the 128MB size, on my machines.  Again,
that size may definately NOT work for you.

PEAK RAMDISK UTILIZATION: 28%
Time of Peak Utilization: 11:46

MAX NUMBER OF MIMEDEFANG MILTERS
      40 Max Allowed
      36 Busy
      36 Loaded

MIMEDEFANG "MILTER" PROCESSING TIME TALLIES
Shortest time to process: 1ms
 Longest time to process: 39649ms
 Average time to process: 1803ms

AVERAGE MESSAGE SIZE: 54 KB

SMALLEST MESSAGE(S)
	Size: 1 Byte
	Msg=i2QFnFGv007270

LARGEST MESSAGE(S)
	Size: 19255646 Bytes
	Msg=i2QGdlBh023803

AVERAGE RATE - MESSAGES PER MINUTE
  MIDNIGHT-8AM: 36
       8AM-5PM: 80
  5PM-MIDNIGHT: 32
       24 HOUR: 51

TOP 10 BUSIEST MINUTES:
  210 Msgs/Min @ 10:25
  189 Msgs/Min @ 10:26
  171 Msgs/Min @ 12:55
  149 Msgs/Min @ 11:08
  148 Msgs/Min @ 10:27
  144 Msgs/Min @ 11:22
  138 Msgs/Min @ 05:00
  136 Msgs/Min @ 08:40
  133 Msgs/Min @ 10:23

So... take the recommendation in the FAQ to heart, but then if you fully
understand the nature of your mail flow, scale it back to a more reasonable
number if the nature of your mail-flow allows.

KEN CORMACK, RHCE
Sr. UNIX Systems Analyst,
    Open Systems Group
Sr. Software Analyst,
    TSG Midrange Systems Group
AFFILIATED COMPUTER SERVICES, INC.



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