How long will your digital data last?
How long will your digital archives last? It's a question I attempted
to answer
back in our April print
issue, and I came up with the following table,
drawn from a number of sources...
Estimated storage life for media stored under ideal conditions.
It seems I was a little optimistic. According to the French National Centre for Scientific Research discs "designed to last for centuries, actually rarely lasted longer than 5 to 10 years." In the most severe cases "the data on some discs lasted just one year."
It seems that buying name-brand discs is no guarantee. "Disc production varies. In the same brand we find discs produced by different manufacturers which means their quality and how long they last for is not necessarily the same."
So what are we to do? The best advice is to be vigilent:"Every two or three years ... copy your archive onto fresh discs. And after that, because these new discs will last a bit longer, you will have to re-copy them after five or six years."
|
Media |
Usable life (years) |
| CD (factory pressed) | 25 |
| CD-R (cyanine and azo dyes | 8-10 |
| CD-R (phthalocyanine dye, gold metal layer) | 100 |
| CD-R (phthalocyanine dye, silver metal layer) | 25 |
| CD-RW, DVD-RW, DVD+RW | 8-10 |
| DVD (factory pressed) | 25 |
| DVD-R, DVD+R | 20 |
| Flash drive | 10 |
| Tape - Analogue | 20 |
| Tape - Digital | 10-15 |
Estimated storage life for media stored under ideal conditions.
It seems I was a little optimistic. According to the French National Centre for Scientific Research discs "designed to last for centuries, actually rarely lasted longer than 5 to 10 years." In the most severe cases "the data on some discs lasted just one year."
It seems that buying name-brand discs is no guarantee. "Disc production varies. In the same brand we find discs produced by different manufacturers which means their quality and how long they last for is not necessarily the same."
So what are we to do? The best advice is to be vigilent:"Every two or three years ... copy your archive onto fresh discs. And after that, because these new discs will last a bit longer, you will have to re-copy them after five or six years."
And spread your archives around: "You must have your information in two places at least -- on a hard-disc, for example, and on another hard-disc or on a recordable DVD or CD."
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Comments
I use three systems. A continuous backup using a simple 1TB WD NAS, Mozy every couple of days, and an external USB drive that I do an entire hard-drive dump to once a month and take to work.
To lose everything Mozy needs to fail at same time as my work and home burn down or on the night that I have the USB drive at home to copy to.
Posted by: charles murphy | June 10, 2010 10:59 PM
Never use optical disks for any sort for backups. As you have found out Geoff, they are just plain unreliable. Instead I have an old pc/server with a bunch of 1TB drives in it. My data is always copied to more than one drive, and often on 3 drives and/or multiple machines. Also USB Hard Drives. stashed at different premises. Lets face it, a house fire will destroy your backups as well as your current data.
The drives are replaced at 2-3 year intervals (staggered so it doesn't hit the wallet all at once). Its the best method I've found so far.
Posted by: chris | June 10, 2010 5:34 PM