How long will floppy disks maintain data integrity?

Question

This was on CNN today:

The U.S. is still using floppy disks to run its nuclear program

Which led me to read through this article:

Think the floppy disk is dead? Think again! Here’s why it still stands between us and a Nuclear Apocalypse

In particular, this excerpt got me thinking:

Last year, a broadcast of 60 Minutes surprised many viewers with the discovery that 8-inch floppy disks were still the preferred method of removable storage for the computers in a U.S. Air Force nuclear silo.

Even the newest 8" floppy disks must be around 25 years old (at least). Honestly, I don't remember floppies being the most-stable storage media to begin with. I can't imagine the old 8" disks have a very good service life. And I remember being able to only reformat a bad disk a few times before it was useless.

While I'm not exactly sure about the Air Force's use case, I'll pose a simple question:

Can you take these disks off the shelf 30 years later and still expect to read their data?

Answer 1

There are a few factors:

1. Quality of media.
2. Storage environment (i.e. climate controlled versus humid attic).
3. How many hours of use did the disk experience.

Assuming little-to-no use, it probably comes down mostly to quality of the floppy disk media which tends to vary across manufacturers and even production year. The formula wasn't always consistent for a brand; I've got old Maxell 5.25" disks of the same model from 1983 which are a distinct mocha color versus a darker brown starting in 1985.

While 5.25" disks seem to have held up over the years, I can say that 3.5" disks were obviously cost reduced and of much lower quality. Some that I have in my collection that were sold as "high quality" back in the early 90's are questionable today at best while a repurposed America Online 3.5" from the same period is almost certainly not going to still hold its original contents.

In general, I think it is hard to come up with an answer for this since nobody really seemed to perform studies on this back in the day; probably because nobody assumed the technology would still be in use 30 years later. However, I will state that you can visibly see if a disk is "dead" physically by looking for small dark spots on the medium (not referring to mold but natural oxidation). If you see that, I'd say you've got time to image the disk before throwing it away and then perhaps cleaning your drive head.

Answer 2

Can you take these disks off the shelf 30 years later and still expect to read their data?

Yes.

Although we all experienced floppies fragility, the magnetic media in fact is one of the longest-living we can practically manufacture. Typical streamer tapes are often guaranteed for 30 years. Of course, under very strict handling and storage conditions - but the point is that no other popular writable media can come even close to 30 years figure. Home and office floppies fail due to mishandling, physical damage, being put too close to speaker, getting dirty, etc - all those failure modes are well known and easily preventable with procedures.

The usage of one of the oldest, 8" floppies is also not surprising here. They have pretty small capacity compared to their size - the largest ever are barely 1.2MB. This gives them tremendous advantage in reliability, as with wide and sparse tracks there is huge margin for error.

Even the newest 8" floppy disks must be around 25 years old (at least).

Do not underestimate the power of a large, government organization. Eg in Poland one agency put on a tender for 130000 3.5" floppies in... 2008. $40k budget. Brand-new ones, manufactured in same year, of course. It's expectable that Navy alone kept one factory afloat for all those years.

And last but not least: You've assumed that they wrote those disk 30 years ago and never touched them since. I believe that's not reasonable assumption. In long-term data storage there are procedures to cyclically read and re-write data on new storage.

/edit: On a second thought, this is just another example of an old tech being continuously used in professional environment despite newer tech being widespread among consumers. NASA using magnetic-core memory in 80's, cars using relays instead of solid-state to control starter motor, Amtrak using rotary converters, etc, etc. The main point is not about absolute reliability, it's about better understanding of failure modes. When you have good understanding of failure modes, you can simply overengineer that particular aspect or put in procedures to circumvent the problem. Being able to predict it with good certainty is all that it takes to achieve the best possible reliability.

Answer 3

The short answer is that they will retain data integrity as long as they do. Floppy disks have a number of enemies: Moisture, corrosion, mildew, deformation of the physical media, degradation of adhesives and other materials, magnetic fields, etc.

If a floppy disk is treated like a precious document and stored in a UV-proof, temperature and humidity controlled environment, free from harmful magnetic fields, and if the bonding agent that keeps the magnetic material attached to the disk surface doesn't fail, the disks may last for decades yet to come even if they are 8" floppies from the 1970s.

However, I've seen floppy disks fail just a couple of months after opening the package. It's a fragile media.

The best advice is to preserve the contents of any floppy you come across if the data contained within is at all worth preservation. Multiple redundant copies remains the surest way to keep data safe into the future.

The US nuclear program has a problem in that the data on those 8" floppies may not exist elsewhere, and we cannot know how long the media or the drives will last. Moving parts eventually fail too, after all. Theoretically the US government could commission new drives and new media at considerable expense. You and I probably cannot do that. But better it would be I think for them to prepare for a day when that fragile media no longer exists.

Answer 4

From something I read just the other day on the news:

"We regularly read floppy disks from 40 years ago and they are as good as new," he said. [someone at The National Museum of Computing at Bletchley Park]

"Magnetic tape has a real issue because when it is on the reels you have a lot of different layers so you have 'print through'," he said. "This involves the shadow of data on one section of tape being superimposed on the layer above and below. The interference means data quickly gets harder to read."

Source: BBC article

Certainly from my own experience, well stored 3.5 inch floppy disks are readable after 20 years, if not more.

Answer 5

When recently imaging my old Amiga disks, dating from 1989 until about 1993, approximately 80% of them read first time without error, another 10% needed a few retries to get all the data off, 9% had unrecoverable sectors, and 1% appeared to be completely unformatted. (The latter were not virgin blank disks, since they were labelled with their contents.)

This is for 3.5" DD disks. Other sizes and densities will of course vary, with 3.5" HD disks being famously awful.

Answer 6

I know I'm responding to an old post here but I though I would share my recent experiences. I recently purchased a TEAC 5.25" floppy drive off eBay for the purpose of going through a bunch of old 5.25" disk that I have (some were mine originally, others come from a bunch I bought at a thrift store a long time ago). I've gone through about two dozen double density disks (some single sided, most double sided but all formatted as double sided it seems) and all of them have been readable so far. These disks date back to between 1983 and 1988. It seems like double density disks can be very reliable for long periods if properly taken care of. I don't know how high density disks compare...I haven't run across any of those yet.

Answer 7

With floppies the density of data write is a big difference. My experience is the more dense data is written the lower the lifetime.

I still got around ~100 of 5.25" DD 3M floppies which last I check (after 15 years of non usage) where still in tact (I did a full backup to HDD and only single disk was a problem but that disc was faulty even back in the days...). On the other hand the average lifetime of 3.5" HD floppy is one year tops. The 5.25" HD floppies where not much better. So I would expect that 8" Floppy properly stored would be still in tact even after 30 years. Also even faulty Floppy is good as new after proper low level reformat (not the MS-DOS crappy one) if no mechanical damage is present.

As written in the other answers Floppies are the most reliable removable storage in longterm. Here empiric experience of mine:

medium    | reliable_storage
--------------------------
MG tapes  | 10  years (reusable)
5.25" DD  | 15+ years (reusable)
3.5" DD   | 10+ years (reusable)
5.25" HD  | 5.0 years (reusable)
3.5"  HD  | 1.0 year  (reusable)
CD W      | 10 years  (fully destroyed metalic layer)
DVD W     | 0.5 year  

So guessing/extrapolating to 8" SD 30+ Years is a real possibility

The closer the tracks are together the sooner they noticeably interact similarly to tapes. Yes of coarse the higher density uses much a bigger B punch so they should be less susceptible to background magnetic fields but the experience tells us a different story.

Well yes we have USB Flash now which can store data for a long time (if not rewritten) but the reliability of the electronics involved is questionable. As for any modern electronics the lifetime goes to hell. I remember electric devices that last for 40+ years. Even my ZX clone from 1989 is still functional. And the modern ones are up to 2-5 years tops...

Answer 8

Even for disks which have self-erased due to entropy, high temperature storage, or poor chemistry resistance to self-demagnetization, these disks are not necessarily defective.

If the magnetic coating has not itself degraded or detached from the plastic, then a self-erased disk can still be used again by low-level reformatting of the entire disk, which lays down new magnetic patterns that defines new data boundaries for tracks and sectors.

(Due to differences in head width and signal strength for low and high density drives, a full erasure with a powerful "bulk erasure" magnet is preferred before low-level reformatting to remove any such old patterns.)

This "refreshing" of the magnetic domains was a feature of an old PC DOS hard drive maintenance software for early MFM/RLL/IDE hard drives, called SpinRite by Steve Gibson. It could read weak sectors, attempt statistical recovery through multiple rereading, and then rewrite each sector to refresh the magnetic patterns.

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EDIT: I should mention that really old hard drives used stepper motors to position the read/write heads. A stepper always turns a precise number of degrees for each step, which would be used to position the heads for each track. But due to the loose mechanical nature of these hard drives, there was some "slop" in the head positioning. Taking an old hard drive and tipping it 90 degrees on its side could lead to read/write errors unless it was low-level formatted for that new physical orientation.

Also external physical impacts could cause the heads to "skip" to a new location, which the stepper can not detect and then leads to the drive being confused about where it is reading or writing. If this track-skipping occurs during a write, it can lead to catastrophic data corruption.

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An improvement over this was the use of optical encoders and the voice-coil servo positioner. There was a clear glass or plastic band with tiny black stripes printed on it, attached to the head positioning arm, and passing over a light sensor.

If the drive head were to be struck and head misalignment occurred, it would immediately detect the misalignment due to the motion of the optical encoder, then stop whatever it was doing and reposition the heads back over the correct track again.

This worked well, but there is a limit on how precise the optical encoder can be, as tracks became ever smaller and smaller as capacity increased. These drives could also still be low-level formatted due to the external optical track positioning sensor.

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At some point there was a transition to a new way of positioning the heads, using special magnetic markers read by the heads to tell them exactly where they are now on the platters. These position markers are printed onto the platters at the factory using special external equipment, and it is not possible to reconstruct the markers once the drive has left the factory. This positioning method is used by all modern hard drives.

Early drives using this method would dedicate an entire platter surface to the servo data, but for modern drives, the permanent servo positioning data is mixed in among the regular read-write areas of each platter, and the drive electronics make sure to never overwrite that servo data.

At this point it became impossible to do true low-level formatting because if the markers are removed, the drive has no idea where anything is on the platters and it becomes useless.

Also, this is why modern hard drives can not be "degaussed" using a powerful external magnetizer, as this removes the head-positioning servo data and the drive can no longer find where tracks are located.

Answer 9

In 2021, I can attest that at least 3.5 Floppy Discs are still viable, though not practical. However, as an electronic musician, and also a fan of obselte and rare " retrotech ". So many people in my genre ( vaporwave and those adjacent ) sometimes use 3.5 Floppy Discs to create physical pressings of albums, as a novelty/collector's item. I myself have released a few. Complete with printed labels and all. And I have tested the discs at various intervals, and out of the new old stock I had from my last release [ 50 multi-colored discs ] only 1 was defective. All of them were unused, btw. Now, that could be on the rare side, and the person I got them from collects these types of older technology ( kinda my " tech " dealer if you will ). They had these stored in a climate controlled building, in a thick plastic bin, sealed in its packaging. So, I know this is like optimal circumstances. But only one dud out of 50 pieces of 30 year old stock, are not that bad of odds. These were from the late 80's to early 90's, so they aren't like the 1970's types. But yeah, maybe not the best for like nuclear codes, but it makes one hell of an aesthetically pleasing album. However, having to compress a half gigabyte of data into 1.44MB storage format, makes the sound quality absolute rubbish. But, you don't exactly by a floppy album for the music quality. It's more for the nostalgia, and uniqueness. Happy thoughts!