From: Gustav Foseid <gustavf-squirrel@in...> - 2000-02-18 12:01:31
I spoke to friend of mine yeasterday which is a sysadmin at the local
university. They have a central unix system serving approx. 20.000
They are currently running a webmail system based on IMP and are having a
scaleability problem. For those of you that are not used to large systems,
a Unix system is sclaing pretty well to somewhere between 5.000 and 10.000
users in a university without very tmuch trouble. If you are getting more
than 10.000 users you need to have a more complex system. The domain here
is stud.ntnu.no (http://www.stud.ntnu.no/).
Here they have 3 fileservers (Sun Ultra 450) which are also IMAP-servers
for the users which have home directories there. There are a bunch of
Pentiums running FreeBSD are working as IMAP-proxies so that everyone can
contact imap.stud.ntnu.no instead of fileserverX.stud.ntnu.no.
The webserver is yet another Ultra 450 (with 2 CPUs an 1GB memory). It is
worth noting that the configuration of Apache and PHP is sub optimal at the
In this configuration it turned out that IMP, which in its design is not
that different from SquirrelMail. The large number of TCP-connections this
is causing is making the system choke.
One solution to make this work could have been to make a appliaction server
running besides the webserver having persisent connections to the IMAP
server. This applications server one could use Unix domain sockets to
I am telling this story not to say that this is something we should do in
SquirrelMail (well maybe for 3.0), but just to say something about how
systems that are working nicelye with many users (like 1000) might not work
as well with very many users (20.000).
Gustav Foseid, Initio IT-løsninger AS