E-Mail systems are the backbone of today’s communication with companies. High available mail services are a must have to ensure the well-running of companies communication. In many IT environments Microsoft exchange server are used. With open source Linux tools an easy and quick HA Cluster can be created. Costs for expensive appliances can be avoided. Companies can rely on the reliability of Linux systems, which ensure that all exchange services are highly available.

1. Open Source in comapnies
Exchange HA Cluster with open
source tools

2. Purpose
• High availability Exchange
Cluster
• When a server failure occurs,
the other server shall take
over all connections
• Load-Balancing shall reduce
the workload on the
individual servers
Quelle: CC by mzeuner – http://farm3.staticflickr.com/2044/1491186958_0313858e3c_b.jpg

3. The IT environment
• 2 Exchange Server
• Provide exchange mail databases
• srvexchange01.foo.bar – 192.168.0.101
• srvexchange02.foo.bar – 192.168.0.102
• 2 Microsoft CAS (Client Access Server)
• Provide all associated mail functionalities
• Such as IMAP/POP and Active Sync
• srvcas01.foo.bar – 192.168.0.111
• srvcas02.foo.bar – 192.168.0.112
• Currently all connections are directed to the first CAS
system, neither load-balancing nor HA takes place
between the systems

4. Visualization of the Environment

5. Solution for HA
• 2 Linux servers with HAProxy and Heartbeat
• Through Heartbeat a shared IP (192.168.0.110) is
created
• HAProxy directs all connections on defined ports to
the CAS systems
• It further does load-balancing between the systems
on a round-robin basis

6. Solution for HA – Visualisation

7. Technical details
• The solutions has been realized with CentOS
• If one HAProxy Server fails, the remaining one takes over
the supplied shared IP
• Active connections are switched automatically to the
remaining active system
• If one of the CAS systems fails all connections are
redirected to the remaining active server

8. Configuration- HAProxy
• Konfiguration HAProxy Dienst (/etc/haproxy/haproxy.cfg)
listen Exchange2010 192.168.0.110:80
bind 192.168.0.110:135
bind 192.168.0.110:110
bind 192.168.0.110:25
bind 192.168.0.110:139
bind 192.168.0.110:443
bind 192.168.0.110:60000
bind 192.168.0.110:60001
bind 192.168.0.110:6001-6004
bind 192.168.0.110:993-995
mode tcp
option persist
balance roundrobin
stick-table type ip size 10240k expire 30m
stick on src
server srvcas01.foo.bar 192.168.0.111 weight 1 check port 80 inter 5000 rise 2 fall 3
server srvcas02.foo.bar 192.168.0.112 weight 1 check port 80 inter 5000 rise 2 fall 3
option redispatch
option abortonclose
maxconn 40000

9. Configuration- Heartbeat
• Configuration of Heartbeat service (/etc/ha.d/ha.cf)
• Configuration of Heartbeat service (/etc/ha.d/haresources)
• Configuration of Heartbeat service (/etc/ha.d/authkeys)
keepalive 2
deadtime 10
udpport 694
bcast eth0
mcast eth0 239.0.0.1 694 1 0
ucast eth0 srvhaproxy01.foo.bar # insert name of the other node here
logfacility local0
node srvhaproxy01.foo.bar
node srvhaproxy02.foo.bar
srvhaproxy01.foo.bar 192.168.0.100
auth 2
2 sha1 loadbalancer-ha

10. Conclusion
• An expensive HA appliance can
be avoided
• The installation is based on
Linux default tools and can
quickly be realized
• There are no changes necessary
to the existing Microsoft
Exchange environment
Quelle: CC FutUndBeidl – http://farm6.staticflickr.com/5199/7369580478_92ccf6bfbd_b.jpg

11. Do you have further questions or
suggestions?
…. Just contact me!
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