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DD, HD and ED floppy disks have individual materials to match their densities.

But is density their only difference?

Are there any differences regarding:

  • Maximum allowable rotation speed?
  • Rewrite cycles?
  • Sensitivity to external magnetic interference?
  • Life span? Data preservation?
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    Are you a floppy disc anorak? – Solar Mike Jan 15 '18 at 15:51
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    Reliability of floppies is well was poor - when I was doing my final year project, each time I saved it was on a different disc. I had a srack of 4 and rotated through them in turn. Over the weeks of my project I binned about 20... and replaced each one binned with a new one. Oh, we used to buy single sided in boxes of 100 and use a hole punch to make them double... typical of engineers... – Solar Mike Jan 15 '18 at 15:57
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    @SolarMike "we used to buy single sided in boxes of 100 and use a hole punch to make them double" ...that sounds like it might have had something to do with your experiences regarding poor floppy disk reliability. I used floppy disks extensively in the late 80s and first half of 90s (roughly) and while I did end up needing to throw away a few, I definitely don't recall ever having to throw away anything like two-digit numbers of floppies in a few weeks. Of course, I didn't use a hole punch on them either... – a CVn Jan 16 '18 at 10:19
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    @TechLord as you can gather from my post, these were not the most reliable but what we had - and the stress of a final year project getting lost was not negligible... One of my friends had to spend 24hours retyping his due to a disc failure with no backup... So my 4 copies - overkill perhaps but there you go. – Solar Mike Jan 16 '18 at 13:55
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    @TechLord well I remember using MG tapes that was even more fun/chalenge/nightmare ... as you would need to tweak the volume and head position (to adjust so the sound is right) and pray not to got CRC error message .... after 5 minutes of loading – Spektre Jan 16 '18 at 15:43
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Hope we are talking about Feromagnetic data storage mediums (like tapes or floppies). Not an expert in the field but:

  1. Maximum allowable rotation speed?

    In general Yes different material means different adhesiveness and structural integrity so you can stress them only up to a point which is different for each material or shape of the medium. This affects the maximal speed and GForce which the medium will survive without degrading. But the speeds used for floppies are too small to even get near these effects. As it is limited by the mechanical properties of the drive and energy consumption and speed of processing. So the answer to this question is not really.

  2. Rewrite cycles?

    No as you are not mechanically changing anything. The only problem may be the substrate material. That is usually some plastics which can age if exposed to radiation (in long therm) and different material/density means different radiation levels. But too these effects usually surface long after the lifetime of the medium. So the answer to this question is not really.

  3. Sensitivity to external magnetic interference?

    Most definately Yes. Different material/density means different size of the head and level of the B field. The higher energy needed to magnetize the lower the sensitivity to external magnetic field. But as experience over last decades show us when you increase the density you increase the auto remagnetization from neighboring tracks/layers. So higher densities lead to better resistance to external fields at cost of lower resistance to data stored nearby on the same medium and usually in favor of the latter (as more dense mediums have smaller life span).

  4. Life span? Data preservation?

    Yes see How long will floppy disks maintain data integrity?.

    On top of that different material can and usually do age at different rate.

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