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Larry Medina's picture
Larry Medina

For the Record

CDs, Lies, and Magnetic Tapes

As I've heard said many times, "... the more things change, the more they stay the same ..."

This article regarding the sensitive nature of media and options for long term storage of information goes a long way towards pointing out the obvious, and something RIM Professionals have been trying to convince people of for years now. 

"Unlike pressed original CDs, burned CDs have a relatively short life span of between two to five years, depending on the quality of the CD," Gerecke said in an interview this week. "There are a few things you can do to extend the life of a burned CD, like keeping the disc in a cool, dark space, but not a whole lot more." The problem is material degradation. Optical discs commonly used for burning, such as CD-R and CD-RW, have a recording surface consisting of a layer of dye that can be modified by heat to store data. The degradation process can result in the data "shifting" on the surface and thus becoming unreadable to the laser beam."

There's nothing that beats the establishing of a sensible media migration policy, one that takes into account not only the usage pattern and methods for storage of media, but considers the value of information being stored on the media.  And there are a FEW more things you can do to extend the length of time you can access information stored on CDs, such as burning a second copy that is stored in optimal environmental conditions, not using pens to write on the surface of the media, not applying adhesive labels to them, and keeping them in their jewel cases.

However, the problems don't stop with the media itself.  Consideration needs to be given to the formats the information is stored in, and ensuring you are able to have persistent access to the format, at minimum, equivalent to the time it's required to be retained.  There is also the issue of hardware obsolescence to consider.  It's imperative to ensure the hardware used to acces the information on the media remains viable for the assigned retention period as well.

The article goes on to recommend the use of magnetic tape as a better case alternative,

"To overcome the preservation limitations of burnable CDs, Gerecke suggests using magnetic tapes, which, he claims, can have a life span of 30 to 100 years, depending on their quality. "Even if magnetic tapes are also subject to degradation, they're still the superior storage media," he said."

... but there are other considerations related to magnetic tape also.  Tape is very sensitive to heat, magnetic fields and dust.  It also needs to be stored vertically, and periodically retensioned.  Care needs to be take to ensure the wall adjacent to the area where tapes are being stored isn't an elevator bay or a switchgear room, both of which contain large magnets and magnetic fields.  And consideration should be given to housing the tapes in six-sided cabinets, properly rated for the protection of media and that they are protected with gaseous based fire protection.

He also correctly points out the need to be ever diligent in the protection of information and not relying on things to remain as they are forever:

"But he's quick to point out that no storage medium lasts forever and, consequently, consumers and business alike need to have a plan for migrating to new storage technologies. "Companies, in particular, need to be constantly looking at new storage technologies and have an archiving strategy that allows them to automatically migrate to new technologies," he said. "Otherwise, they're going to wind up in a dead end. And for those sitting on terabytes of crucial data, that could be a colossal problem."

But the fact that the recommendation being made is to go backwards to an older, less technological alternative, such as magnetic tape over CDs and even hard drives indicates we shouldn't be too quick to jump to untested technologies!

Larry Medina

What People Are Saying

I have often wondered about this

I've wondered about this ever since I bought a spindle of cheap CompUSA CDRs. After a year the CDs were unreadable. I have found the ones that I did store in a drawer held up a little better. After reading the article with Kurt Gerecke comments, it does give me some insight to what I have thought all along.

At the present, I never archive any of my data. I usually do backups onto a separate server. I do also make it a habit to replace all my hard drives every 3 years. It does sound expensive, but so is my data.

Yes, thou live in an analog

Yes, thou live in an analog world in which our machines can discern oughts and noughts at sweet and fast high density.

Entropy brings its chaos to thouest universe like heat, increasing disorder in all.

That which is made of the fewest atoms suffers more dearly under the cruel handmaiden of chaos' dynamo. Otherwise large objects made of many atoms will remain throughout with less disorder to the whole over the same amount of passing time.

Re the earlier comments that

Re the earlier comments that digital tape has a short life because we've all seen how VHS and audio tapes degrade after only a few years -- you're comparing apples and oranges. VHS and audio cassette are analog recordings that rely on accurate preservation of a continuous range of real-time signal levels; any signal degradation will likely be noticeable. Computer tapes are digital recordings that only have to preserve two discernable signal levels for "0" and "1"; even a very degraded signal may be perfectly readable as long as the signal's transitions across binary threshold levels are intact. Then, even if the occasional bit or two does get messed up, the encoding method almost always provides a degree of error correction.

Hi! Please read the link

Hi!

Please read the link below for Cnet's perspective on this.

http://asia.cnet.com/reviews/hardware/storage/0,39034915,39091141-1,00.htm

ER

I stopped making photo

I stopped making photo albums with 4x6 prints when I converged to digital photography last year. Guess I should go back to making those prints, just in case ...! :-(
Regards,
Anders H

One thing is certain, a

One thing is certain, a properly processed black and white photographic negative (NOT color transparancy or negative) lasts well over 100 years, even under less than optimal storage conditions.

I have cd-r stored in my

I have cd-r stored in my garage and where the moister and temperateur are unstable, and they still are readable after 5-6 years

The "Life Expectancy of

The "Life Expectancy of Storage Media" was discussed in the 9/20/1999 issue of Computerworld. The article discussed the results of a testing and a literature search of life expectancy testing. P22 contained a chart on the "Life Expectancy of Storage Media" resulting from the authors work (sorry I didn't record their names). It showed a 2-20 year expectancy for CD-R's. The expectancy, 100-500 years, was for Archival paper. Various types of Mag tapes had expectancies of 2-30 years. Modern paper self distructs - anyone have yellowed paperbacks? I wonder if Larry could locate and re-post the article.

I forget the exact number/definition, but life expectancy means something like 98% of an "thing" will last that long or longer. So its no surprise that so many folks have not had a problem... but then I do recall my 3.5 inch disks, with good handling, that failed to read after a few years... :-)

bob e v

I'd like to see a magnetic

I'd like to see a magnetic tape last 30 years (forget 100years!) without dropouts... I wonder what the author used to test his theory?

A few years ago I read a

A few years ago I read a 9-track mag tape that was created 20 years before on a mainframe. We just got the data transferred (it only covered a few percent of the tape) before the oxide started flaking off. The tape had to be thrown out. I have a classical music CD that was produced, and it started skipping: clean surface, no physical damage, not a scratch. Haven't lost any recordable CDs yet if they were successfully burned. Flash memory is not a good idea for long-term retention. Maximum is about ten years. The charge leaks through the thin oxide insulator. I've seen some that lose data in weeks or months (but can be rewritten). Hard disks are very variable. We have some that are over 12 years old and have been running 24/7 and others that fail right out of the box, and every thing between. Having them sit around too long without running might not be so good either. They might not start up when needed. The more important the data, the more redundancy, care and attention needed.
-- computer engineer in New Jersey