On Sun, 30 Jan 2000, Omer Efraim wrote:
> Actually, this whole conversation got me to thinking
> about how a lot of large-scale pop servers (in particular)
> are doing it all wrong(?), and about how one can probably
> come up with a quick hackjob that would scale much better
> than traditional pop servers (not only scale better, but will
> give better performance on even the most basic hardware).
if you want to check on improving a situation, you first need to check
exactly what is the situation - i'm not suer that the current method, of
forking off a process for each connection, is very problematic - the life
time of the process is much larger then the ammount of time it takes to
fork it off (i.e. you often take a minute or a few minutes to download
email - the fork operation takes less then one 10th of a second - now, is
_this_ where you should optimize??).
it sounds to me like a better place for optimization is storing compressed
email messages - it'll take more CPU power when storing the email, but you
could set up a capabilities system in which the client will speicy if it
can handle compressed email or not, and if it can, the decompression can
be done on the client side. this compress could make download time
smaller, and thus allow the server to support more clients. ofcourse,
there's a need to check which part takes longer - downloading the letters,
or compressing and decompressing them.. also note that this compressiong
will save up on I/O operations needed to save/load the letters, so it
might be that the compression itself is usefull even if the letters are
still sent to the clients in a non-compressed format... measurements are
needed here....
> I'm thinking about a qmail specific scenario (as this is the
> MTA I'm most familier with), but I'm sure this applies to
> other MTAs as well.
well, with qmail you got one advantage that you don't have with sendmail
(for instalce) - the usage of mail dirs. when you have all mail stored in
one large file, the pop server needs to copy this email folder back and
forth when servicing the client. when using mail directories - this
copying operation is not required (unless a letter is not downloaded, and
rather has its UIDL data updated - anyone can tell if in qmail the header
and the letter's contents are stored in a single file, or in two seperate
files?)
anyway, that's what i think.
guy
"For world domination - press 1,
or dial 0, and please hold, for the creator." -- nob o. dy
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