Gmail, i think Google’s Gmail is of the most popular and widely used email service provider. Most of the people are using Gmail for email facilities, including the website owner by using gmail’s free service called “Google Apps“. Gmail is popular because of there awesome interface, banner less presentation, very less advertisements, almost no images, huge storage space, etc etc.
Have you ever imagine how the Gmail provides 7 to 8 GB of space for free ? day by day thousands and millions of people are signing up for Gmail and billions of emails are sent and received through out. so how this is managed by Google ? Whats the secret ?
Actually Google is using a concept called “Cloud computing“. Whats that ?

Cloud computing is an umbrella term used to describe the use of computing services that are hosted on a network (typically the internet) and used by PCs (or other devices) without having to specify specific servers or systems.
Source : BPC on Cloud computing

Using Cloud computing Google can easily extend there storage space and processing power over the cloud of computers so that when ever they need more they just spread there network to wide area and hence they can easily provide you huge storage without failure.

Now most of the email providers, video sharing sites like Youtube, document sharing sites, file sharing sites are using cloud computing to provide best and maximum facilities to there users.