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?
  • A very important difference between disk standards is the possible (or, for slow computers: required) data rate to and from the floppy. One of the important metrics of magnetic storage is average access time (positioning the magnetic heads onto a specific sector), the other is the data transfer rate.
    – tofro
    Commented Jan 15, 2018 at 16:02
  • 1
    @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
    Commented Jan 16, 2018 at 15:43

1 Answer 1


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.

  • Generally to-the-point answer, regarding 3 I would say that a magnetic field strong enough to affect the weak DD 5.25" and the strong DD 3.5" is enough to affect any magnetic media. The magnetic field would have to be strong and changing, such as being near a speaker of at least 20W which is playing sound. Regarding 4 storage is everything, and that dust and mold will not affect any coating; when cleaned the information is readable as new. A not physically damaged coating resists information change according to coercivity value and original write signal strength fulfilling that. Commented Aug 16, 2023 at 17:30
  • @HenrikErlandsson time shows that magnetization is changing also from lower than coercitivity threshold fields over time that is what #3 is mostly about if your have 2 tracks of magnetic coding closely packed/placed together they tend to magnetize its neighbors over time. IIRC This was firstly detected on old MG and VHS tapes after long storage creating shadows and "noise" ... no alternating field or movement is required for this to take effect
    – Spektre
    Commented Aug 17, 2023 at 8:07

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