Global Load balancing solutions

As I have received some questions about GLB I will try to answer some of them here.

What is Global Load Balancing?

Global load balancing is a concept where several data centers answers to a web site.

In its simplest form you can create a GLB by using DNS to point to the IP address of your different web sites. This way you can share the load between your data centers.

But often you want more. Today most modern GLB solution can give you more:

• Direct you to the closest data center (based on IP addresses). (Speed.)
• Make sure the data center is up and running before sending clients there. (Always up.)

And probably more as well.

Most load balancers, if not all, uses DNS to direct traffic. The GLB is basically a DNS server that checks the incoming request and makes intelligent decisions before returning an answer.

This page talks about why GLB does not work. I do not agree to everything on this page but you will have to make out your own mind.

What GLB is not

With GLB you only get the solution to distribute traffic between your data centers. You still have to solve database replication, how to maintain your files in sync and so forth.

Who are the players?

I have done some research and found these vendors. I have not tried any of the solutions, only read the product documentation. I am sure there are other players, but they are sometimes hard to find.

Player	Comment
F5 Big-IP GTM	The most expensive solution I have found. I have used F5 products before and they usually work well. You can only buy this as an appliance. You can choose to buy it as a GTM only or as a local traffic management (load balancer) with GTM on top.
Zeus ZXTM GLB	You can buy this as an appliance or as a VMWare image. Promises good performance, supports active-active data centers and you can make rules on how to route traffic.
Coyotepoint Envoy	Envoy is an add-on to their local load balancer appliance. That is - you need to buy everything from them. With Envoy you can create policies for traffic management.