Our aim in this recipe is to build an architecture where our customers accede to one unique server, but this server is able to balance requests on other servers depending on their current load.

Each server belonging to the second layer of servers is an exact replica of your Magento server. You can either reinstall your web server and Magento on each one or ask your hosting company to deliver you an exact replica of the old one. The real work is on the front server, the one to which your customers accede. We have to install a piece of software called reverse proxy in order to forward requests from this frontend server to every backend server.

Open a new terminal and enter the following command:

sudo apt-get install pound

Then edit the file named pound.cfg in the /etc/pound/ directory so that it looks like the following code:

ListenHTTP
  Address 10.0.0.1 #FRONT SERVER ADDRESS
  Port 80

  Service
    BackEnd
      Address 10.0.0.2 #MY FIRST BACKEND SERVER
      Port 80
    End
    BackEnd
      Address 10.0.0.3 # MY SECOND BACKEND SERVER
      Port 80
    End
    #REPEAT BACKEND BLOCKS FOR EACH SERVERS
  END
END

Enable the frontend server to start by modifying the value of Startup in /etc/default/pound as follows:

Startup = 1

Then start the frontend server using the following command and it will switch from one server to another, depending on the load:

Sudo /etc/init.d/pound start

The idea behind this well-known technique, named load balancing, is to get one server in front of the others and for that server to redirect users to the least loaded servers at that moment. Moreover, you have web servers behind this one; so each of them will be less loaded.