Archiving onto CDs

STORING DATA ON CDs: Nigel Deacon

In about 2005 I wrote an article about CD longevity and the suitability of CDs as a storage medium. Now, several years and many discs later, I am in a position to give an update.

This is a personal view based on my experience of using around 1,000 CDs (CD-R) over a period of thirteen years to store copies of large mp3 files. I do not claim any special knowledge or expertise. The data are limited; I am merely reporting observations made since early 1998.

The discs are stored in an upstairs room, on shelves, vertically, mainly in plastic envelopes, out of the light, in an open but shaded cupboard.

None of the discs are sticky-labelled; I use spirit-soluble ink on the reverse side.

So - my update.....

ARCHIVING ONTO CD

I have found that CDs are not suitable for long-term storage or archiving. The claims of 80-year lifetimes sometimes seen on sales literature are largely fictitious. They are based on 'accelerated ageing' tests which do not relate very well to reality.

CDs are not suitable for storing old photographs, audio files, or anything else of real value.

CD-Rs are best regarded as a way of getting data off one computer and onto another - say by post - when you don't want the expense of buying a memory stick.

If you're giving important data to a company, or a recording or set of photographs to a friend, be aware that a CD may go blank within a small number of years.

My figures below are for discs carefully stored, catalogued and used regularly. For CDs left in an office or around the house, in CD players, on windowsills, on desks, on the tops of filing cabinets, etc., the lifetime will be reduced, especially if in sunlight. As a chemist I'd guess a CD left on a sunny desk, out of its envelope, wouldn't be readable after six months.

My recommendation for archiving is to store on an external hard drive, with a backup onto another hard drive of different make. For really important material, consider reciprocal exchanges with other people having a shared interest in the data.

'Cloud' storage is also worth considering - on remote servers, but this may be pricey.

MY OBSERVATIONS: CD LONGEVITY (APPROXIMATE):

IMATION: 10% failure rate in 3 years; 75% unreadable after 10 years
TEVION: 10% failure rate in 2 years; none readable after 10 years
MAXELL: 10% failure rate in 5 years; 30% unreadable after 10 years
TDK: 2% failure rate in 10 years
VERBATIM: 2% failure rate in 10 years
MISC UNBRANDED: 10% failure rate in 3 years, with enormous variability; some discs OK after 12 years; others fail after six months.
RE-RECORDABLES: these sometimes hold data for less than six months. If you want to store data from a re-recordable disc, my recommendation is to copy it straight away.

CONCLUSIONS

I don't have enough experience of other brands to estimate how long they last. However, Sony appears similar to Imation, Fuji looks similar to TDK, and Pengo looks similar to Verbatim.

Some disc failures can be predicted from the disc appearance - slight discolouring of the reverse side of the CD near the outer edge. Hold the disc so the light reflects into your eyes.

It's not all negative; CDs have their uses, and will be around for a long while yet. The message is : don't use them inappropriately.

There are no easy answers when it comes to data storage. If you must put sound or photograph files on CD for long-term future use, I suggest:

1. Don't throw away your originals (tapes, cassettes, reels, black and white original prints, etc).

2. Inspect regularly, and re-burn valuable items. If you can't bear to do this, make multiple copies on different brands of CD and keep them in different locations; for example, give them to your friends).

3. Regard CDs as a temporary "transfer" medium only.

Nigel Deacon / Diversity website

Footnote:

.....I am in touch with a number of people who use large numbers of CDs for storing mp3 files. One reports that he has experienced a 25% failure rate after five years with a batch of blue TDK CD-Rs.

Another reports more success with CD-RWs than CD-R (no details of brand, unfortunately), and a similar failure rate using DVD and CD-R.

A person from the BBC contacting me two years ago reported 100% failure of Sony CD-Rs after 10 years storage in plastic CD boxes in a lightproof cabinet.