Posey's Tips & Tricks
The Big Paradox -- Why Did Abused Media Survive?
My decades-old floppy disks defied harsh attic conditions, raising questions about media durability, bit rot and long-term storage assumptions.
The year was 2006. I was preparing to move to a new home and needed to figure out what to do with a bunch of old floppy disks. I thought about throwing them out since they were already old, but since I didn't have time to sort through them all, I simply packed them into plastic storage bins. Somehow, those plastic bins found their way into the attic at my new home, where they remained completely untouched for the next 20 years.
Recently, I rediscovered these disks and decided to take a chance and see if any of them still contained readable data. To my complete astonishment, nearly all of the disks were in perfect condition. The question is, why?
The way that the disks were stored violated nearly every best practice imaginable. In the attic, they were exposed to 20 years of heat, humidity, and dust. There were huge thermal cycles ranging from below freezing in the winter to an estimated 150 degrees in the summer. The disks spent decades without spinning or being refreshed and the plastic storage bins were likely also a source of static.
Most of the disks are at least 30 years old, with a few being over 40 years old. I would have assumed that bit rot would have stolen all of the data and that the disk's lubricants and binders would have broken down over the years, completely compromising the disk's structural integrity. Against all odds though, nearly all the disks survived. And I'm not just talking about being able to read the directory. I have been copying disks to modern media and have been playing decades-old video games!
As you can imagine, my head was spinning with all kinds of questions. Have we been lied to about bit rot and media storage best practices? Did I just get lucky? And what are the implications for modern removable media such as backup tapes?
In an effort to wrap my head around the situation, I reached out to a friend who has an IT background and asked him what he thought. Initially, he told me that I probably just got lucky and had purchased some exceptionally high-quality disks. That answer might be valid if my collection consisted of half a dozen disks, but I probably have close to a thousand. While I admit I have not yet tested every single disk, I have been through over six hundred disks and so far only about 5 have failed. My friend also suggested the idea of survivorship bias. But that theory doesn't hold up either.
After giving the question a lot of thought, I think that there are two reasons why well over 99 percent of the disks that I have tested survived.
Imagine that a media company in the 1980s is about to start selling 5.25-inch floppy disks. They have absolutely no way of knowing how durable the disks will truly be. At that point, the format is still brand new. There are no 40-year-old floppy disks that can be tested. That being the case, all the engineers can do is to perform various tests and extrapolate the results to come up with a predicted lifespan. However, history is filled with situations in which products ultimately end up being far more durable (or far less durable) than what they were supposed to be.
Of course, those engineers probably also lowballed the life span estimates. Imagine for a moment that the engineers performed some tests and concluded that the disk would likely last for 15 years (I am just making up a number). If the media companies marketed the disks as having a 15-year lifespan, but the disks failed after 10 years, then everyone would be upset. If on the other hand, the media companies marketed the disks as having a 10-year lifespan, but they lasted for fifteen, then nobody complains.
Even if my theory about manufacturers grossly underestimating the lifespan of a floppy disk is correct, it still doesn't explain how my disks remained viable after decades of being stored in the worst possible conditions. However, I have a theory about that too.
My guess is that it comes down to the way that the magnetic flux is stored on the disk. Consider a modern HDD (spinning media hard drive). Such a drive can accommodate multiple terabytes of data in a 3.5-inch form factor. This means that the bits have to be packed very tightly into the available physical space. Now consider a floppy disk from the 1980s. The disk only holds 360 KB worth of data (or up to 1.2 MB if it's a double-sided, high-density disk). That 360 KB is spread out over 5.25 inches of space. That means that the sectors have a comparatively large physical footprint and that might help the disk to retain magnetic flux, even after all of this time.
Obviously, bit rot is a real phenomenon, and media should always be stored in a way that adheres to the manufacturer's recommendations. Even so, it seems like our understanding of long-term media degradation might be incomplete.
About the Author
Brien Posey is a 22-time Microsoft MVP with decades of IT experience. As a freelance writer, Posey has written thousands of articles and contributed to several dozen books on a wide variety of IT topics. Prior to going freelance, Posey was a CIO for a national chain of hospitals and health care facilities. He has also served as a network administrator for some of the country's largest insurance companies and for the Department of Defense at Fort Knox. In addition to his continued work in IT, Posey has spent the last several years actively training as a commercial scientist-astronaut candidate in preparation to fly on a mission to study polar mesospheric clouds from space. You can follow his spaceflight training on his Web site.