Hard disks can't be feeling very happy these days: from music to movies, email to invoices, we're increasingly storing our important data in the cloud.

Now that reliable and fast broadband and mobile broadband are available to most of us, the lure of the cloud is getting stronger – and it's being helped by a price war between competing cloud providers.

What's so great about the cloud?

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Convenience.

You're probably already using a cloud-based email service such as Gmail, Outlook or similar, so you'll be familiar with the idea of accessing it on whatever device happens to be handy: your smartphone, laptop, tablet, or even a borrowed PC in a hotel lobby.

Cloud computing brings that convenience to everything. Instead of transferring media files to your phone you simply stream MP3s or movies from faraway servers.

Instead of copying crucial documents to flash drives or burning them to disc, you stick them in the cloud where they can't be left in the office or on a train.

Even more conveniently, much of this happens automatically – so for example cloud-based music services know when you've bought new music and make it available to all your devices immediately, and cloud-based storage knows when you've updated a file and updates its copy accordingly.

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What are the downsides?

The cloud isn't much cop without an internet connection, although most services enable you to download files for times when you won't be able to get online.

 Some services are limited to specific hardware, although that has become less of an issue since Apple launched iCloud Drive as part of iOS8.

There are also financial considerations. Cloud services generally have multiple tiers, with a free service for casual use and paid-for versions for more serious or demanding users. As you'll discover, there are huge differences between the various providers' prices.

Dropbox

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Dropbox has over 300 million users, saving a billion files every day, 4 million business customers, of which 80,000 are corporate one.

The firm has supplemented its file and folder APIs with data APIs, enabling mobile app developers to share data as well as files over the service.

That's important because, unlike some rivals, Dropbox is multi-platform. You can install it on a Mac or PC, on a BlackBerry or a Kindle Fire, on an iPhone or iPad or Android device.

You can use it to sync and access music files, photos or movies, or you can use it as a hard drive in the sky, or you can use it for any other kind of content.

For example, apps such as  Scrivener and Onenote writing programs work with Dropbox so all your notes and scribbles are available from any device.

Dropbox's very nature as a multi-platform provider means it is constantly making moves to remain relevant and the past six months has seen plenty of activity when it comes to Microsoft Office. Among the features that have already been implement are the ability to collaborate on Office documents across Windows and Macs using Dropbox plus users can edit the same documents inside Office Online.

Add this to the new apps for Windows tablets and smartphones and the fact that Dropbox for iOS will soon allow you to edit Office documents inside the app without leaving, and you get to see why so many still opt for Dropbox over other offerings.

Microsoft

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Microsoft's been doing the cloud computing thing for decades: Hotmail (later Windows Live Hotmail, and now Outlook.com) was one of the first web-based email services, and Microsoft bought it back in 1997 when nobody really knew what cloud computing was. Its Azure platform powers many big businesses, and Xbox Live brought all kinds of entertainment to the Xbox.

When Google Docs first appeared, Microsoft didn't see it as a threat, but that belief has clearly changed. Today, Microsoft offers a range of cloud-connected Office services including the free Office Web Apps and the subscription-based

Office 365

Like Google, Microsoft has been revising its various cloud offerings, so for example its Live Mesh file syncing service was retired and replaced with SkyDrive. Legal action from Sky forced a name change, and SkyDrive is now known as OneDrive.

OneDrive is rather similar to Google Drive: you can use it to share and synchronise files between different devices, and you can create Word documents, Excel workbooks, PowerPoint presentations, OneNote notebooks and Excel surveys inside your browser.

In an aggressive move, Microsoft has dramatically increased the OneDrive storage from 7GB to 15GB for free users, and to a whopping 1TB for Office 365 subscribers.

 If you don't want to subscribe to Office, extra storage is $1.99  per month for an additional 100GB.

OneDrive apps are available for Windows Vista onwards, for the Mac, for Windows Phone, Android and iOS, and like Google Drive there are also third-party apps that can use OneDrive for synchronisation. Examples include sketching apps, document scanners, PDF managers, notepad apps and document signing apps.