The world's stock of data grew 62% last year.

According to The Guardian, we've squirreled away 0.8 zettabytes of data. That's 800,000 petabytes, where each petabyte is a million gigabytes. Somewhere along the way we forgot about exabytes (1000 petabytes).

By the end of this year we'll be sitting on 1.2Zb.

It's a lot of data.

But as I've previously reported, almost all the data stored around the world is worthless junk. Experts say as much as 90% of stored data is useless.

We're not talking about trash tv or bad music. We're talking about data that is of no use to anyone; useless files, duplicate data, temporary files that became permanent.

Forget everything you hear from businesses selling virtualisation as a green technology. If the so-called green computer makers really wanted to use less electricity and save the planet, they'd be working on tools to de-duplicate files and data and applications to help us cull rubbish from our hard drives.This would also make it easier to find the good stuff.