If you are planning to scale your website to accommodate for extra traffic on the website.You have two options you can scale vertically or horizontally.
Vertical scaling usually involves adding extra ram/processing power which may be desired,but there is a limit to this kind of scaling.
Horizontal scaling is were you setup multiple machines and they work together to get the work done.Haproxy is loadbalancer which will let you scale your infrastructure horizontally.
To setup loadbalancing between 2 machines is pretty simple.Firstly you will require two machines with static address or a DNS entry to identify the machines.
I will using vagrant during this process of setting up a loadbalancer.I will be using vagrant a virtual machine environment which does have a gui.More information about it can be found at http://vagrantup.com/.
I have setup up virtual machines running ubuntu 13.04 LTS.Both the machines are running Apache2 with default settings.You can replicate the same by running this on the terminal.
sudo apt-get update sudo apt-get install apache2 php5 sudo apt-get install libapache2-mod-php5 sudo service apache2 restart
Next we get the ip address of the two machines and store them someplace safely.
The ip address of machine one is 10.0.2.2 and the second machine is 10.0.2.3.
We them launch another vm with haproxy.
Run sudo apt-get install haproxy
This will install haproxy with default settings.
Next to start haproxy as service we have to enable it in the configuration file.
vi /etc/default/haproxy ENABLED=1 sudo service haproxy restart
Next we haproxy to point to the two servers we setup earlier.Next we move the original configuration of haproxy and keep it as a backup.
sudo mv /etc/haproxy/haproxy.cfg /etc/haproxy/haproxy.bak
We then create our own configuration file with
sudo vi /etc/haproxy/haproxy.cfg
Add this to the cfg file.
global log 127.0.0.1 local0 notice maxconn 2000 user haproxy group haproxy listen appname 0.0.0.0:80 mode http stats enable cookie SRVNAME insert balance roundrobin option httpclose option forwardfor server server1 10.0.2.2:80 check server server1 10.0.2.3:80 check
Once this is done a quick restart of haproxy and the haproxy acts as the frontend for the incoming traffic.