On Sat, 4 Sep 1999, Robert Kelsey wrote:
> If an average list has 100 members, how many lists can I host before I run
> out of hours in the day delivering the messages? How much bandwidth is
> involved in this?
> Is it possible to host 1,000 lists on one server and be able to deliver
> mail promptly?
do you really mean bandwidth, or are you asking about processing load?
whichever you mean, the answer remains the same: your main constraint is
likely to be the bandwidth of your network connection
consider:
1 list x 100 members x 10 messages/day x 1 kbyte avg. message size =
1 mbyte of traffic per day = 8 mbit/day = approx. 93 bits/sec.
if you have a 56kb network connection, a fast computer, and all 10
messages arrived at the same time - they'd all go out within a few seconds
for 1000 lists, you're up to 93kbit/sec. - if all you have is a 56kbps
line, you're in big trouble - mail will just keep backing up until your
queue overflows, if you have a 128kbps connection, it will be 73% loaded
(if all messages were to show up at once, it would take 17 hours to get
them out)
note:
if your average message size is larger (e.g. if people routinely send
large file attachments) then you'll need more bandwidth: for the previous
example, if your average message size jumps to 10kbyte, then you'll need a
T1 line to keep up
if a lot of messages go to the same destination host (e.g. aol), and your
mailer is smart enough to send these only once (with a large to: list),
then your bandwidth needs go down
even if your host has a fast connection, upstream routers can be choke
points - e.g., if your machine has an ethernet connection to an office
LAN, but your company's connection to the outside world is only 56kb.
----
Processing load is less of an issue.
While a full analysis involves the speed of your machine, how much memory
and disk space you have, the speed of memory and disk i/o, what mail
transfer agent you're running, etc., any reasonable machine can handle the
load you're describing.
For the above examples:
1 list x 100 members x 10 messages/day x 1 kbyte avg. message size =
1000 messages per day, 1 mbyte per day
pretty much any machine can handle this
1000 lists x 100 members x 10 messages/day x 1 kbyte avg. message size =
1 million messages/day, 1 gigabyte/day
this still doesn't seem like much of a system load:
1 million messages per day / 86,400 seconds per day =
11 messages/second - this doesn't seem like much of a load for a fast
machine that's primarily handling mail (on a 1 mip machine, each message
gets almost 100,000 instructions)
and a gigabyte/day doesn't represent all that much disk i/o
even if your average message is 10kbyte, it would seem that your network
connection is still the bottleneck:
1000 lists x 100 members x 10 messages/day x 10 kbyte avg. message size =
10 gbyte/day = 116 kbyte/second - well within the memory i/o and disk i/o
transfer rates of any reasonable machine
References:
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