Configuration of a Load-Balanced and Fail-Over Merak Cluster using
Windows Server 2003 Network Load Balancing
Author: Gerrit Schunk Last Modified: 2005-07-08
Table of Contents
Table of Contents ... 2 Introduction ... 3 Requirements ... 4 Configuration ... 5 Windows Configuration... 5 Merak Configuration ... 10 Appendix A: DNS Configuration ... 12Appendix B: Merak ODBC Configuration ... 12
Introduction
This guide provides basic step-by-step instructions on how to configure a simple load-balancing and fail-over Merak cluster using Windows Server 2003 Network Load Balancing.
This type of cluster configuration is suitable for small- to mid-sized installations that require basic fail-over support. It is not suitable for high volume installations that primarily need load-balancing between several servers.
Only a minimal configuration is described, advanced topics (such as database connectivity via ODBC) are not covered is detail.
Requirements
• Good understanding of Windows Server 2003, TCP/IP and Merak.
• Two or more severs running Windows Server 2003 Standard/Enterprise. Each server must have two NICs, at least one in each server must be support by Windows Load Balancing (see Appendix C). • One license of Merak Professional 8.20 or later for each server.
• A common storage system connected to all servers. This could be, for example, a NAS or SAN. • One Public IP address for the entire cluster.
• One Public IP address for each server.
Configuration
Windows Configuration
1. Install Windows Server 2003 on all machines. Active Directory is not required. The machines should be called MX1, MX2, etc. Make sure the shared storage system is working correctly.
2. Configure two network connections on each machine. A Public Cluster Connection and a Private Cluster
Connection:
It is recommended that both network connections are connected to different switches. The Private
Subnet should not be accessible from the Public Subnet and vice-versa.
3. Configure the Private Cluster Connections on all machines. Assign each machine a different private IP
4. Configure the Public Cluster Connections. Assign the same IP address to each machine the (i.e. 10.0.1.10):
• Select Network Load Balancing in the network settings of the Public Custer Connection:
Enter the same public IP address and Subnet mask on all machines. The Full Internet Name must reflect the machine name (i.e. mx1.mail.domain.tld, mx2.mail.domain.tld, etc.). The Cluster
operation mode must be set on Unicast.
Each machine must have its own Priority (unique host identifier). This number should be the same as the number in the machine name. Do not assign the same number to multiple machines.
It is recommended, but not required, to assign to each machine a second public and dedicated IP address (i.e. 10.0.1.11). Enter this IP address and subnet mask in the Dedicated IP
• Once you click on OK, you will see this message:
• Click on OK and select Internet Protocol (TCP/IP) from the list. Configure the network interface
with the same Public IP address, Subnet Mask and Default gateway on all machines. The
Preferred DNS server and Alternate DNS server can be same on all servers, but if you run the
After entering the public cluster IP address and the DNS server addresses, click on Advanced… and add the dedicated public IP address:
5. Close all network configuration dialogs by clicking on OK.
Merak Configuration
1. Install Merak Professional 8.20 or later on all machines.
2. Open the Merak Administration program on each machine and configure Merak to use the shared storage system (if some options are not visible you may have to switch to the Advanced interface mode):
• Select Merak Mail Server > System > Storage.
• Change the Mail path so that it points to a directory on the shared storage system:
The Temp path and Log path should be kept on the local machine. It is recommended that you enable the option Use mailbox path alphabetical sorting.
The Config, Forward and Retry paths must point to the shared storage system. The other paths depend on the type of your installation.
In Server ID enter the machine name of each server and in Hostname enter the FQHN of each machine.
3. Restart all machines.
Appendix A: DNS Configuration
The entire cluster shares one public IP address, and the DNS records should only point to this IP address:
mail.domain.tld. IN A 10.0.1.10
pop3.domain.tld. IN A 10.0.1.10
smtp.domain.tld. IN A 10.0.1.10
domain.tld. IN MX mail.domain.tld.
You should also add a DNS entry for each server that points to the dedicated public IP address: mx1.mail.domain.tld. IN A 10.0.1.11 mx2.mail.domain.tld. IN A 10.0.1.12 mx3.mail.domain.tld. IN A 10.0.1.13 mx4.mail.domain.tld. IN A 10.0.1.14 mx5.mail.domain.tld. IN A 10.0.1.15 etc.
Reverse DNS (PTR) records should also be added for each dedicated public IP address and the cluster
public IP address.
Appendix B: Merak ODBC Configuration
If you want to use ODBC to store the configuration in database, you should install Microsoft SQL Server (or any other supported database server software) on two machines connected to the private cluster subnet. These two machines can be the same ones that Merak is installed to. In any case make sure that the database sever software is not accessible from the Internet.
If the database server software is installed on the same machines as Merak, you may want to switch the Primary connection and Backup connections on one of the machines:
Configure the two database server to synchronize/replicate the two Merak databases. Consult the database sever documentation for details.
Appendix C: Checking NIC Compatibility
You can use the tool CHKNIC.EXE from the Windows Server 2003 Resource Kit Tools to verify that your NICs are compatible with Windows Network Load Balancing:
