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How to use Windows Network Load Balancing to load balance Exchange 2010

Posted by Alin D on November 13, 2011

When administrators consider load balancing their Exchange 2010 installations, they often turn to dedicated — and frequently expensive — hardware products. Fortunately, if you’re Linux-savvy, a free load-balancing option is available. If not, that’s alright, help is on the way.

You can use Windows Network Load Balancing to load balance Exchange, but several limitations make it impractical for certain Exchange deployments. For example, you can’t add more than eight nodes in a Network Load Balancing cluster. You also can’t combineWindows Failover Clustering and Network Load Balancing because they can’t interact with each other.

In cases like these, you need external assistance. Help usually comes in the form of hardware-based load balancers. Unfortunately, those products aren’t cheap. Prices typically start around $1,500 for low-end models and quickly soar into the tens of thousands of dollars.

Most companies don’t have to spend that kind of money though. You can use a free virtual-software appliance that acts as a load balancer. This appliance can be installed on a repurposed server or even in a virtual machine (VM) on shared hardware. All you’re really “spending” is the time and effort to get it up and running.

Your free load-balancing options for Exchange 2010
One such appliance is HAProxya Linux-based Layer 4 load balancer for TCP and HTTP applications. There are already a number of third-party products like redWall’s Firewall and Exceliance’s HAPEE distribution that use the tool, as well as many satisfied users — the Fedora Project, Reddit, StackOverflow and many more.

You must be comfortable with Linux to use HAProxy in your Exchange 2010 production environment. If not, Microsoft-certified systems administrator Steve Goodman created the Exchange 2010 HAProxy Virtual Load Balancer.

The appliance is a pre-packaged version of HAProxy, built on Ubuntu Linux, that can be deployed on VMware vSphere orMicrosoft Hyper-V with minimal work required by an Exchange administrator.

All you need is a solid understanding of your network topology and some familiarity with either VMware or Hyper-V. While you don’t need to fully understand Linux to install Goodman’s appliance, it does help to know about the OS if you want to fine-tune aspects of the tool that aren’t available through the Web interface. That said, you can get the HAProxy Virtual Load Balancer up and running in your Exchange 2010 lab environment without being a Linux expert.

The appliance comes in two formats: a VMware vSphere .ovf file and a Hyper-V-compatible .vhd file. The tool’s website contains step-by-step instructions on how to set up HAProxy on either vSphere or Hyper-V.

Setting up the Exchange 2010 HAProxy Virtual Load Balancer
Boot the appliance and you’re greeted with a simple console login screen. To begin, type inroot as your username and setup as your password. You will be prompted to choose a new password. This secures the setup process; you can change the password later on.

Next comes the most important part of the setup. You must set the IP address, netmask and default gateway for HAProxy. If you mistype anything, press Ctrl+C to get out of the script, type logout to leave, then log back in. Remember to use your new password, then repeat the login process. After you complete the first step, you will be given a URL; make sure to write it down. You will be prompted to log back in when HAProxy reboots.

The rest of the setup process — as well as most HAProxy management — is done through HAProxy’s Web interface. Configure the static RPC ports for your client access servers, then list the IP addresses of each of the client access servers you want to balance. You must also set the time zone and the network time protocol (NTP) servers. Don’t touch the console login screen unless there’s an overwhelming reason to do so.

While the HAProxy Virtual Load Balancer has been through plenty of development, the virtual appliance is still a work in progress. For example, HAProxy is a Layer 4 (TCP) balancer, not a Layer 7 (application-level) balancer. It is not completely “Exchange-aware,” so it can’t do things like application-level monitoring or SSL offloading — at least, not yet.

These items may eventually be added, and it sounds like Goodman plans to further improve the tool. ”Subsequent versions will be production ready, as this is totally aimed at being an easy-to-use free alternative to paid-for hardware and virtual load balancers for Exchange 2010,” Goodman said.

 

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