Author: Kjetil Torgrim Homme Date: To: ppp2005 CC: exim-users Subject: Re: [exim] Recommendation - Separate Servers? Cluster? Round Robin?
On Tue, 2005-05-17 at 15:24 -0300, ppp2005@??? wrote: > We have 8.000 user accounts increasing 500 monthly.
>
> Our first server run Exim 4, Spamassassin and Clamav and it's a Dual
> Xeon 2.4 with 1.5 Gb memory and Scsi 36Gb disk.
>
> Now we need to put a 2nd server, but I don't know the better choice to
> future, anyone can helpme?
>
> 1 Option: Cluster
> - 2 servers in cluster
> - 1 storage Scsi
>
> 2 Option: Separete Servers
> - 2 completely separete servers, with your own users
>
> 3 Option: Round Robin in DNS
> - 2 servers with a round robin configure in DNS to distribute load
I recommend that you avoid NFS, at least. it will become a bottleneck
which is hard/expensive to scale up.
in our solution we have three servers running Cyrus. they're connected
to a SAN, and a Cyrus instance can fail over to another server during
maintenance or problems since all the state is mountable from the SAN.
Exim and SpamAssassin is running on a separate set of servers, but since
they don't do final delivery, they are completely independent of
eachother. we use a loadbalancer (LVS with keepalived) to distribute
the load, but DNS round robin would work fine for this, too.
it can be a bit of a pain that the users are spread across the Cyrus
instances, of course. we have a good user database system keeping
everything in sync, so this isn't very painful for us. but you may not
need this complexity yet.
my recommendation is to split the tasks in two, so the new server is a
pure delivery server running IMAP and POP service. you may find that
your third server needs to be a receiving server, since SpamAssassin
etc. is so CPU-intensive. that third server can then be added alongside
your current server with very small changes to your system.
--
Kjetil T. (University of Oslo)
