Many people will disagree with me when I say the cloud is just a server. Clouds can be classified as public, private or hybrid, but that is what it really boils down to it is a machine or set of machines providing services over the web. Certainly you can argue that cloud can provide infrastructure, platform, and the traditional application services. Talked about some of these services in earlier articles.
However the internet is a network of systems that can be clearly defined. In the systems on the network can be described sort of like a road map or a set of telephone lines connected like below.
It may not be important exactly how they are put together, except that we know they are there. To know who is where either by what is known as a web address or an ipaddress (sort of phone number) allows you to access part of the cloud that you wish to connect to. It is impossible to know every phone number or ipaddress by heart, so the internet has a built in phonebook known as a Domain name server (aka dns). So when you type in www.google.com the dns translates that name into 126.96.36.199 and the networking equipment connects to Google for you. The dns can also assign phone numbers. Why is that important?
Since a cloud can be as simple as one server, you could actually have a cloud in your own home or office with just a desktop and another computer. Generally the device that hooks you to the internet sort of acts like a local dns or telephone book.You can actually have several computers work together without having to actually access the larger real world internet.
You can have your own mini internet, but it is usually known as an intranet. With in that intranet you can set up your own server or servers just like the real internet. With your local servers, you might not even know the difference. You can use fancy expensive equipment to be your cloud servers, but to be honest, most any home computer like the one below will work just right.
Older computers are perfect for being a web server. In fact, on our web server, it has several sites that can be accessed from just one machine, just like they do in the real world. Those are known as virtual sites. For more information see: http://www.instructables.com/id/Uses-for-your-own-private-cloud/
Today many people use what is known as embedded devices to act as servers. They have a smaller foot print and use a lot less energy. We use the Cisco Linksys NSLU2 converted to run linux.
The Raspberry Pi, Beaglebone Black, Pogoplug, and a variety of devices can also be used. It is not how big your system is, it is how you use it.