A guide to online storage and backup services

Most of us are used to installing applications on our PCs and saving the files and documents they create to our hard disk. In cloud computing, the software that creates and saves files runs on an internet server (‘cloud' is just a jargon term for the internet) and it's often possible to store files online.

All you need to interact with these services is a web browser such as Internet Explorer or Firefox. Some require you to install an application that enables your PC to talk to the internet server directly.

Many types of service come under the umbrella term ‘cloud computing', but in this article we are particularly interested in the ones that allow for online storage and backup. In this guide we are going to explain how they work and why they are useful.

Put a copy in the post
It's possible that you are already doing some computing in the so-called cloud. Webmail services such as Windows Live Mail and Gmail are essentially email programs that operate entirely from servers on the web.

Gmail and Windows Live Mail also offer an easy way to back up files, as both services provide a relatively generous amount of storage space free. Gmail currently allows more than 7GB and adds to this every year.

The simplest way to use Gmail for backup is to send an email to your own address with an attachment, such as a collection of photos. Once sent, the email and attachments are safely stored.

There's another way to take advantage of the free storage capacity provided by Gmail, and that's using a free tool called Gspace, which automates the transfer of files and documents to your Gmail account without having to fiddle about with emails and attachments. There are versions for Windows, Linux and Apple OSX.

Photo-sharing sites such as Picasa and Flickr also fit the cloud description. While their prime aim is to enable people to share photo collections with friends, a copy of the images is stored online so it's a good way to keep a simple backup. As photos can be among the most precious files stored on a computer, having more than one backup is a good idea, and Picasa and Flickr offer a free and simple way to keep one more copy.

Keep in sync
With the services we have mentioned so far, backup is more of a side effect but there are also lots of cloud services that make backing up your precious files their primary purpose.

Online backup services offer three useful features. The first is that after the initial process of uploading files to the server is complete, the software ensures that only files that have been changed or newly created are copied to the server. This kind of technology, called incremental backup, is already in use in software that creates a backup on external hard disks.