If you’re the owner of any albums on compact disc going back to their release in the early 1980s, you might have recently noticed that the tracks don’t play as well as they used to.

Similarly, games and software that were purchased in the 1990s on CD-ROMs (or even some DVD-ROM titles from the past few years) might have become difficult to play, resulting in you scouring eBay for a replacement or trying to track down a reissue (if the game was particularly good).

DVD movie titles, too, seem to have suffered from aging – but what exactly is going on here? When first released, CDs and DVDs were said to be “indestructible” – save for scratches, the content on them should last forever.

Yet over the past few years it has been shown that manufacturing faults and fungus have been able to destroy data, leaving CD- and DVD-ROM backups made by home users over the past 15 years potentially useless.

So what can we do to get around this problem?

Eaters of Data

There are two key causes of data loss on optical discs: manufacturing faults where the reflective, metallic layer comes away from the plastic disc, resulting in unreadable media, and the bizarre, “surely-an-urban-legend-but-no” oxidized metal surface-eating fungus.

While the fungus occurs largely in equatorial regions, it seems to have spread since its first discovery nearly ten years ago, and has been chomping away at original and home-burned optical discs around the world. You might think that this could be a neat way of getting rid of some of the more embarrassing titles in your music collection, but there are bigger considerations.

Namely, if we’ve been backing up data to writable CDs and DVDs for the past 15 years or so, what happens to the data?

At present there is no indication if the fungus is learning songs by Madonna or discovering the names and addresses of Phyllis Sladen’s relatives in Canberra, Australia – as the oxidized metal surface is eaten by the fungus, it spreads, basically doing what fungus does. The data just disappears.

Optical Alternatives

All of which means that we need to start thinking about alternatives to optical storage, and pretty quickly. While Blu-ray is supposedly manufactured to a better standard and less likely to be affected by fungus, the fact is that CDs and DVDs have already succumbed, no doubt involving some adaptation by the fungus from another substance. It is the way of nature that at some point, Blu-ray discs will become appetizing for something.

Clearly, then, optical discs are not reliable for long term storage. There are two good alternatives:

Hard disk drive – maintain an occasionally-used external HDD for keeping a secondary copy of all of your vital data, including, if necessary, ISOs of any software that you have purchased that isn’t available via a service such as Steam.

Regularly updating your optical library – the other choice is to keep copies of your data across multiple DVDs (or writable Blu-ray discs) and update these regularly. For instance your January 2011 update might be replaced in January 2012. This way, you retain the portability of the optical format with control over what gets copied and when.

Hopefully using one of these methods you can avoid losing any optically-stored data in future.