On Mon, 27 Feb 2012 13:38:39 -0500, Charles Marcus <CMarcus@Media-Brokers.com> wrote:
On 2012-02-27 1:34 PM, Sven Hartge <sven@svenhartge.de> wrote:
Charles Marcus<CMarcus@media-brokers.com> wrote:
Each location is an entire floor of a 6 story building. The remote location has the capacity for about 60 users, the new location about 100. We only allow IMAP access to email, so if everyone is using email at the same time, that would be a lot of traffic over a single Gb link I think...
Naa, most clients download mails only once and then keep them cached locally (at least Thunderbird and Outlook do).
Looking at the used bandwidth of the mailserver of my small university (10.000 users, about 1000 concurrently active during the daytime) shows a steady amount of roughly 5MBit/s with peaks to 10MBit/s in and out.
Interesting - thanks for the numbers...
But, again, my main reason for 2 servers is not performance, it is for redundancy...
I too have been tasked with multisite redundancy, and have been experimenting with GlusterFS (http://www.gluster.org/community/documentation/index.php/Main_Page), which is a distributed file system. In our network we have a dedicated 10GB link between two datacenters 100 miles apart, and I have a GlusterFS node at each site setup in Distriubted Replicated mode with 2 replicas which means the servers are mirrored. The file writes are done to all the replica servers (2 servers in this case), so depending on network latency the writes could potentially slow down. GlusterFS has it's own file serving protocol that allows automatic and immediate failover in the case that a storage node disappears, but there are some caveats to restoring a failed storage node (takes forever to resync the data). I have not put this experiment into production, but I can say that it's extremely simple to manage, and performance testing has shown that it could handle mail traffic just fine. You could also look at GPFS (http://www-03.ibm.com/systems/software/gpfs/), which is not open source but it's apparently rock solid and I believe supports multisite clustering.