Why are HDD platters harder than the floppy/ZIP discs?

Discussion in 'Computer Security' started by GreenXenon, Jun 19, 2009.

  1. GreenXenon

    GreenXenon Guest

    Hi:

    I have a question just out of curiosity.

    I notice with ZIP discs and floppies, the disc is a soft dark-brown
    round film-like material that can easily be shredded -- with paper-
    shredder -- to remove confidential information.

    However, the magnetic platters in HDDs are much harder and metallic.

    Why don't they make the hard-disc-drive platters soft like the discs
    of floppies and ZIPs? It would be so much easier to remove unwanted
    confidential information then. Simply unscrew the HDD, remove the soft
    platters and dump them into a paper-shreder.

    To remove personal info from an HDD requires that the platters be
    heated beyond Curie point to eliminate all magnetic data. This is
    extremely inconvenient and dangerous because of the high temperatures
    required.


    Thanks a bunch,

    Green
     
    GreenXenon, Jun 19, 2009
    #1
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  2. GreenXenon

    chuckcar Guest

    GreenXenon <> wrote in
    news::

    > Hi:
    >
    > I have a question just out of curiosity.
    >
    > I notice with ZIP discs and floppies, the disc is a soft dark-brown
    > round film-like material that can easily be shredded -- with paper-
    > shredder -- to remove confidential information.
    >
    > However, the magnetic platters in HDDs are much harder and metallic.
    >
    > Why don't they make the hard-disc-drive platters soft like the discs
    > of floppies and ZIPs? It would be so much easier to remove unwanted
    > confidential information then. Simply unscrew the HDD, remove the soft
    > platters and dump them into a paper-shreder.
    >
    > To remove personal info from an HDD requires that the platters be
    > heated beyond Curie point to eliminate all magnetic data. This is
    > extremely inconvenient and dangerous because of the high temperatures
    > required.
    >

    Several reasons: 1. Rotation speed. Hard drives spin at several thousand
    RPM (7,000-10,000), Floppies at under 500. You can actually tell by their
    sound when a revolution is finished - less than a second, but definitely
    discernable. 2. Head gap. Floppy disk heads sit on the order of 1 mm from
    the surface of the disk and frequently make contact with it. Hard drive
    heads float less than 10 millionths of an inch over the surface and due to
    the speed involved will destroy the surface if they contact it. However if
    you have to do more than a full format, that's only the start of your
    security concerns IMHO.

    --
    (setq (chuck nil) car(chuck) )
     
    chuckcar, Jun 19, 2009
    #2
    1. Advertising

  3. Because if they made "hard" drives floppy like you want they couldn't
    call them HARD drives dimwit!


    "GreenXenon" <> wrote in message
    news:...
    > Hi:
    >
    > I have a question just out of curiosity.
    >
    > I notice with ZIP discs and floppies, the disc is a soft dark-brown
    > round film-like material that can easily be shredded -- with paper-
    > shredder -- to remove confidential information.
    >
    > However, the magnetic platters in HDDs are much harder and metallic.
    >
    > Why don't they make the hard-disc-drive platters soft like the discs
    > of floppies and ZIPs? It would be so much easier to remove unwanted
    > confidential information then. Simply unscrew the HDD, remove the soft
    > platters and dump them into a paper-shreder.
    >
    > To remove personal info from an HDD requires that the platters be
    > heated beyond Curie point to eliminate all magnetic data. This is
    > extremely inconvenient and dangerous because of the high temperatures
    > required.
    >
    >
    > Thanks a bunch,
    >
    > Green
     
    J¡m ßéâñ, Jun 19, 2009
    #3
  4. GreenXenon

    GreenXenon Guest

    On Jun 19, 1:28 pm, "Stephen" <> wrote:
    > This is down to several factors.
    >
    > Typical hard drives are hermetically sealed units which allow the platters
    > to spin at a higher RPM than would be the case for Zip or floppy drives.
    >
    > If the hard disc was "floppy", you will find that it will distort if you
    > start spinning it at 5,400rpm (most laptop drives) or ar 7,200rpm (most
    > desktop hard drives) or even at 10,000rpm (high performance drives) the
    > floppy media would probably tear itself to shreds.
    >
    > In addition, the gap between the read/write heads and the data surface is
    > very tiny, so any accidental bending of the disk surface runs the risk of
    > the heads destroying the data surface and making the owner kiss goodbye to
    > many Gigs worth of data. Having a hermetically sealed disk means there is no
    > issues with dust as there would be on a removable disc.
    >
    > In addition, if the hard disc surface was to increase in diameter with the
    > high rotational speed, the head positioning motors would have to have a
    > tracking compensation algorithm so it knew where the data had "moved" to
    >
    > So thats why hard discs have glass platters with a magnetic coating on it.
    >
    > zip discs and floppies spin at much lower rpm as the disk is not
    > hermetically sealed and to avoid disc distortion that would otherwise occur
    > at higher RPM and also are of lower data density compared to todays HDD's og
    > 500Gb to 1.5TB so head positioning on zip and floppies os not as critical as
    > it would be on a HDD.



    Is it possible to hermetically-seal the soft disc of a floppy/zip? Of
    course the spin speed would still have to be slow to prevent the soft
    material from being injured. Right?

    Is it also true that in order to have the same amount of storage
    space, that the soft floppy material would need to be bigger in
    diameter than the hard platter of an HDD?

    IOW, is it possible for a soft floppy disc to have the same data
    density as a hard HDD platter?
     
    GreenXenon, Jun 19, 2009
    #4
  5. "GreenXenon" <> wrote in message
    news:...
    > On Jun 19, 1:28 pm, "Stephen" <> wrote:
    >> This is down to several factors.
    >>
    >> Typical hard drives are hermetically sealed units which allow the
    >> platters
    >> to spin at a higher RPM than would be the case for Zip or floppy drives.
    >>
    >> If the hard disc was "floppy", you will find that it will distort if you
    >> start spinning it at 5,400rpm (most laptop drives) or ar 7,200rpm (most
    >> desktop hard drives) or even at 10,000rpm (high performance drives) the
    >> floppy media would probably tear itself to shreds.
    >>
    >> In addition, the gap between the read/write heads and the data surface is
    >> very tiny, so any accidental bending of the disk surface runs the risk of
    >> the heads destroying the data surface and making the owner kiss goodbye
    >> to
    >> many Gigs worth of data. Having a hermetically sealed disk means there is
    >> no
    >> issues with dust as there would be on a removable disc.
    >>
    >> In addition, if the hard disc surface was to increase in diameter with
    >> the
    >> high rotational speed, the head positioning motors would have to have a
    >> tracking compensation algorithm so it knew where the data had "moved" to
    >>
    >> So thats why hard discs have glass platters with a magnetic coating on
    >> it.
    >>
    >> zip discs and floppies spin at much lower rpm as the disk is not
    >> hermetically sealed and to avoid disc distortion that would otherwise
    >> occur
    >> at higher RPM and also are of lower data density compared to todays HDD's
    >> og
    >> 500Gb to 1.5TB so head positioning on zip and floppies os not as critical
    >> as
    >> it would be on a HDD.

    >
    >
    > Is it possible to hermetically-seal the soft disc of a floppy/zip?


    Yes, it's possible, but why do it?



    Of
    > course the spin speed would still have to be slow to prevent the soft
    > material from being injured. Right?
    >
    > Is it also true that in order to have the same amount of storage
    > space, that the soft floppy material would need to be bigger in
    > diameter than the hard platter of an HDD?
    >


    Yes. The reason for speed is that the area of a data cluster can be smaller.




    > IOW, is it possible for a soft floppy disc to have the same data
    > density as a hard HDD platter?


    NO, because the floppy spins at a fraction of the speed.
     
    Jeff Strickland, Jun 19, 2009
    #5
  6. GreenXenon

    Rod Speed Guest

    GreenXenon wrote

    > I have a question just out of curiosity.


    Dont forget what curiosity did to the cat.

    > I notice with ZIP discs and floppies, the disc is a soft dark-brown
    > round film-like material that can easily be shredded -- with paper-
    > shredder -- to remove confidential information.


    > However, the magnetic platters in HDDs are much harder and metallic.


    > Why don't they make the hard-disc-drive platters soft like the discs of floppies and ZIPs?


    Because you get much higher bit densitys with rigid platters
    and its completely trivial to wipe them magnetically and you
    can reuse the platters when you do that.

    > It would be so much easier to remove
    > unwanted confidential information then.


    Nope.

    > Simply unscrew the HDD, remove the soft
    > platters and dump them into a paper-shreder.


    Much easier to use a decent security wipe like dban.

    > To remove personal info from an HDD requires that the platters
    > be heated beyond Curie point to eliminate all magnetic data.


    Wrong. All you need is a decent security wipe like dban.

    > This is extremely inconvenient and dangerous because of the high temperatures required.


    Nothing dangerous about a properly designed furnace.

    And shredded floppys have actually been recovered.
     
    Rod Speed, Jun 20, 2009
    #6
  7. GreenXenon

    Rod Speed Guest

    Stephen wrote:

    > This is down to several factors.


    > Typical hard drives are hermetically sealed units


    No they arent. They always have a filtered vent that allows pressure equalisation.

    > which allow the platters to spin at a higher RPM than would be the case for Zip or floppy drives.


    It isnt the spin rate that allows the much higher bit density.

    > If the hard disc was "floppy", you will find that it will distort if
    > you start spinning it at 5,400rpm (most laptop drives) or ar 7,200rpm
    > (most desktop hard drives) or even at 10,000rpm (high performance
    > drives) the floppy media would probably tear itself to shreds.


    > In addition, the gap between the read/write heads and the data
    > surface is very tiny, so any accidental bending of the disk surface
    > runs the risk of the heads destroying the data surface


    In fact hard drive heads fly. Floppy drives heads dont.

    > and making the owner kiss goodbye to many Gigs worth of data. Having a hermetically sealed disk means there is no
    > issues with dust as there would be on a removable disc.


    > In addition, if the hard disc surface was to increase in diameter
    > with the high rotational speed, the head positioning motors would have to have a tracking compensation algorithm so it
    > knew where the data had "moved" to


    Nope, modern hard drives have embedded servo info that handles that
    fine as the platter expand and contract due to changing temperatue.

    > So thats why hard discs have glass platters with a magnetic coating on it.


    They arent all glass.

    > zip discs and floppies spin at much lower rpm as the disk is not
    > hermetically sealed and to avoid disc distortion that would otherwise
    > occur at higher RPM and also are of lower data density compared to todays HDD's og 500Gb to 1.5TB so head positioning
    > on zip and floppies os not as critical as it would be on a HDD.


    In fact the real reason is just the much higher bit densitys possible with rigid platters.


    > GreenXenon <> wrote


    >> I have a question just out of curiosity.
    >>
    >> I notice with ZIP discs and floppies, the disc is a soft dark-brown
    >> round film-like material that can easily be shredded -- with paper-
    >> shredder -- to remove confidential information.
    >>
    >> However, the magnetic platters in HDDs are much harder and metallic.
    >>
    >> Why don't they make the hard-disc-drive platters soft like the discs
    >> of floppies and ZIPs? It would be so much easier to remove unwanted
    >> confidential information then. Simply unscrew the HDD, remove the
    >> soft platters and dump them into a paper-shreder.
    >>
    >> To remove personal info from an HDD requires that the platters be
    >> heated beyond Curie point to eliminate all magnetic data. This is
    >> extremely inconvenient and dangerous because of the high temperatures
    >> required.
    >>
    >>
    >> Thanks a bunch,
    >>
    >> Green
     
    Rod Speed, Jun 20, 2009
    #7
  8. GreenXenon

    Rod Speed Guest

    chuckcar wrote:
    > GreenXenon <> wrote in
    > news::
    >
    >> Hi:
    >>
    >> I have a question just out of curiosity.
    >>
    >> I notice with ZIP discs and floppies, the disc is a soft dark-brown
    >> round film-like material that can easily be shredded -- with paper-
    >> shredder -- to remove confidential information.
    >>
    >> However, the magnetic platters in HDDs are much harder and metallic.
    >>
    >> Why don't they make the hard-disc-drive platters soft like the discs
    >> of floppies and ZIPs? It would be so much easier to remove unwanted
    >> confidential information then. Simply unscrew the HDD, remove the
    >> soft platters and dump them into a paper-shreder.
    >>
    >> To remove personal info from an HDD requires that the platters be
    >> heated beyond Curie point to eliminate all magnetic data. This is
    >> extremely inconvenient and dangerous because of the high temperatures
    >> required.
    >>

    > Several reasons: 1. Rotation speed. Hard drives spin at several
    > thousand RPM (7,000-10,000), Floppies at under 500. You can actually
    > tell by their sound when a revolution is finished - less than a
    > second, but definitely discernable. 2. Head gap. Floppy disk heads
    > sit on the order of 1 mm from the surface of the disk and frequently
    > make contact with it.


    In fact they always make contact and dont fly like a hard drive head does.

    > Hard drive heads float less than 10 millionths
    > of an inch over the surface and due to the speed involved will
    > destroy the surface if they contact it. However if you have to do
    > more than a full format, that's only the start of your security
    > concerns IMHO.
     
    Rod Speed, Jun 20, 2009
    #8
  9. GreenXenon

    Rod Speed Guest

    GreenXenon wrote:
    > On Jun 19, 1:28 pm, "Stephen" <> wrote:
    >> This is down to several factors.
    >>
    >> Typical hard drives are hermetically sealed units which allow the
    >> platters to spin at a higher RPM than would be the case for Zip or
    >> floppy drives.
    >>
    >> If the hard disc was "floppy", you will find that it will distort if
    >> you start spinning it at 5,400rpm (most laptop drives) or ar
    >> 7,200rpm (most desktop hard drives) or even at 10,000rpm (high
    >> performance drives) the floppy media would probably tear itself to
    >> shreds.
    >>
    >> In addition, the gap between the read/write heads and the data
    >> surface is very tiny, so any accidental bending of the disk surface
    >> runs the risk of the heads destroying the data surface and making
    >> the owner kiss goodbye to many Gigs worth of data. Having a
    >> hermetically sealed disk means there is no issues with dust as there
    >> would be on a removable disc.
    >>
    >> In addition, if the hard disc surface was to increase in diameter
    >> with the high rotational speed, the head positioning motors would
    >> have to have a tracking compensation algorithm so it knew where the
    >> data had "moved" to
    >>
    >> So thats why hard discs have glass platters with a magnetic coating
    >> on it.
    >>
    >> zip discs and floppies spin at much lower rpm as the disk is not
    >> hermetically sealed and to avoid disc distortion that would
    >> otherwise occur at higher RPM and also are of lower data density
    >> compared to todays HDD's og 500Gb to 1.5TB so head positioning on
    >> zip and floppies os not as critical as it would be on a HDD.


    > Is it possible to hermetically-seal the soft disc of a floppy/zip?


    Yes, and hard drives arent in fact hermetically sealed anyway.

    > Of course the spin speed would still have to be slow
    > to prevent the soft material from being injured. Right?


    Nope. It would be possible to make flexible
    material that could be spun at those speeds.

    > Is it also true that in order to have the same amount of storage
    > space, that the soft floppy material would need to be bigger in
    > diameter than the hard platter of an HDD?


    Thats true in the sense that the bit densitys are much higher with rigid platters.

    > IOW, is it possible for a soft floppy disc to have
    > the same data density as a hard HDD platter?


    Nope.

    And its all completely pointless anyway when its so completely trivial to
    use a decent security wipe like dban that completely wipes rigid platters.

    The only thing it cant wipe is spared sectors.
     
    Rod Speed, Jun 20, 2009
    #9
  10. GreenXenon

    sandy58 Guest

    On Jun 19, 8:42 pm, GreenXenon <> wrote:
    > Hi:
    >
    > I have a question just out of curiosity.
    >
    > I notice with ZIP discs and floppies, the disc is a soft dark-brown
    > round film-like material that can easily be shredded -- with paper-
    > shredder -- to remove confidential information.
    >
    > However, the magnetic platters in HDDs are much harder and metallic.
    >
    > Why don't they make the hard-disc-drive platters soft like the discs
    > of floppies and ZIPs? It would be so much easier to remove unwanted
    > confidential information then. Simply unscrew the HDD, remove the soft
    > platters and dump them into a paper-shreder.
    >
    > To remove personal info from an HDD requires that the platters be
    > heated beyond Curie point to eliminate all magnetic data. This is
    > extremely inconvenient and dangerous because of the high temperatures
    > required.
    >
    > Thanks a bunch,
    >
    > Green


    Hey, GreenGlow, did you ever get answers to these questions yet?
    What is Sphygmo-thermic dissociation?
    When a neuron is stimulated, it depolarizes. When relaxed, it
    hyperpolarizes?
    They chased you from comp.dsp, sci.physics & sci.med.cardiology for
    being a troll.
    Grow up.....if you are ALLOWED, that is????
     
    sandy58, Jun 20, 2009
    #10
  11. GreenXenon

    Bear Bottoms Guest

    On Sat, 20 Jun 2009 10:43:51 +0100, Tim Jackson wrote:

    > GreenXenon wrote:
    >> Hi:
    >>
    >> I have a question just out of curiosity.
    >>
    >> I notice with ZIP discs and floppies, the disc is a soft dark-brown
    >> round film-like material that can easily be shredded -- with paper-
    >> shredder -- to remove confidential information.
    >>
    >> However, the magnetic platters in HDDs are much harder and metallic.
    >>
    >> Why don't they make the hard-disc-drive platters soft like the discs
    >> of floppies and ZIPs? It would be so much easier to remove unwanted
    >> confidential information then. Simply unscrew the HDD, remove the soft
    >> platters and dump them into a paper-shreder.
    >>
    >> To remove personal info from an HDD requires that the platters be
    >> heated beyond Curie point to eliminate all magnetic data. This is
    >> extremely inconvenient and dangerous because of the high temperatures
    >> required.
    >>
    >> Thanks a bunch,
    >>
    >> Green

    >
    > Very simply, you couldn't make a flexible disk flat enough.
    >
    > The recording density you can get is proportional to (among other
    > things) the gap between the head and the disk surface. To achieve a
    > very small gap HDD heads work on the principle of an air bearing, and
    > fly by ground-effect a tiny distance (tenths of a micro-metre) from the
    > surface. This requires that the surface be incredibly flat, the forces
    > on the head are tiny so the available acceleration to track surface
    > variations is also tiny. To achieve this the disk has to be very rigid,
    > very clean, and precisely machined.
    >
    > When I worked in the business and learned about the "kissing track"
    > where the head hits the disk in order to find it, or lands on it when it
    > stops, I did the calculation of how long it would take the head to reach
    > flying height if it approached slow enough that ground effect would stop
    > it before it hit, I forget the answer now but it was huge, at least weeks.
    >
    > They are sealed (and pressure equalised through a porous filter) to keep
    > out dust, Typical small dust particles are in the order of 10
    > micro-metres, boulder sized on the scale of the gap.
    >
    > If you are worried about possible remnant magnetic data on a disk after
    > it has been wiped, you also ought to be worried about the remnant
    > footprints you leave walking down the street. They are about as easy
    > and reliable to trace.
    >
    > What sort of criminal activity are you into that is worth spending
    > millions to try to dig out these tiny traces of fragmentary data and
    > bring them to a level of proof that would stand up in court, to
    > incriminate you? Especially as you could always argue that it was a
    > factory-refurbished machine and they were left by some previous owner,
    > or that such techniques have a significant chance of creating apparently
    > incriminating data from random noise. Should we even be talking to you
    > if you are that level of bad guy?
    >
    > Tim Jackson


    Thx for the response.

    Pinhead.
    --
    Bear Bottoms-Freeware Researcher Extraordinaire
    Freeware website: http://bearware.info
     
    Bear Bottoms, Jun 20, 2009
    #11
  12. GreenXenon

    Rod Speed Guest

    Tim Jackson wrote
    > GreenXenon wrote


    >> I have a question just out of curiosity.


    >> I notice with ZIP discs and floppies, the disc is a soft dark-brown
    >> round film-like material that can easily be shredded -- with paper-
    >> shredder -- to remove confidential information.


    >> However, the magnetic platters in HDDs are much harder and metallic.


    >> Why don't they make the hard-disc-drive platters soft like the discs
    >> of floppies and ZIPs? It would be so much easier to remove unwanted
    >> confidential information then. Simply unscrew the HDD, remove the
    >> soft platters and dump them into a paper-shreder.


    >> To remove personal info from an HDD requires that the platters be
    >> heated beyond Curie point to eliminate all magnetic data. This is extremely inconvenient and dangerous because of the
    >> high temperatures required.


    > Very simply, you couldn't make a flexible disk flat enough.


    > The recording density you can get is proportional to (among other
    > things) the gap between the head and the disk surface. To achieve a
    > very small gap HDD heads work on the principle of an air bearing, and
    > fly by ground-effect a tiny distance (tenths of a micro-metre) from
    > the surface. This requires that the surface be incredibly flat, the
    > forces on the head are tiny so the available acceleration to track
    > surface variations is also tiny. To achieve this the disk has to be
    > very rigid, very clean, and precisely machined.


    > When I worked in the business and learned about the "kissing track" where the head hits the disk in order to find it,


    That was never the case with PC hard drives.

    > or lands on it when it stops,


    That doesnt happen anymore either.

    > I did the calculation of how long it would take the head to reach flying height if it approached slow enough that
    > ground effect would stop it before it hit, I forget the answer now but it was huge, at least weeks.


    Have fun explaining how hard drive heads fly then.

    > They are sealed (and pressure equalised through a porous filter) to keep out dust, Typical small dust particles are in
    > the order of 10 micro-metres, boulder sized on the scale of the gap.


    > If you are worried about possible remnant magnetic data on a disk after it has been wiped, you also ought to be
    > worried about the remnant footprints you leave walking down the street. They are about as easy and reliable to trace.


    > What sort of criminal activity are you into that is worth spending
    > millions to try to dig out these tiny traces of fragmentary data and bring them to a level of proof that would stand
    > up in court, to incriminate you? Especially as you could always argue that it was a factory-refurbished machine and
    > they were left by some previous owner, or that such techniques have a significant chance of creating apparently
    > incriminating data from random noise. Should we even be talking to you if you are that level of bad guy?
     
    Rod Speed, Jun 20, 2009
    #12
  13. GreenXenon

    Rod Speed Guest

    Tim Jackson wrote
    > Rod Speed wrote
    >> Tim Jackson wrote


    >>> When I worked in the business and learned about the "kissing track" where the head hits the disk in order to find
    >>> it,


    >> That was never the case with PC hard drives.


    >>> or lands on it when it stops,


    >> That doesnt happen anymore either.


    >>> I did the calculation of how long it would take the head to reach flying height if it approached slow enough that
    >>> ground effect would stop it before it hit, I forget the answer now but it was huge, at least weeks.


    >> Have fun explaining how hard drive heads fly then.


    > AFAIK both Contact Stop/Start (CSS) and Loading/Unloading are still in use on PC drives.


    The heads are loaded and unloaded but they do not land on the platter anymore.

    There was never ever any 'kissing track'. What we did see with stepper
    motor head actuator drives was the heads moved against a physical
    stop to recalibrate, but thats not a particular TRACK on the drive.

    > Certainly both have been used on PCs,


    Nope, particularly that original claim about a TRACK.

    > with load/unload now being back in fashion,


    Load and unload is an entirely separate matter to the heads
    landing on the platters when the drive stops spinning. That
    doesnt happen anymore, tho it did certainly happen at one
    time. Thats what stiction is, the heads stuck to the platter.

    > and I am not aware of any "third way".


    There is in the sense that the heads are retracted from the platters at shutdown.

    > If you have an alternative answer please share it,


    I did, I told you that the first never happened, and
    that heads no longer land on the platters anymore.

    > just denigrating my answer does not help anyone.


    It does point out that your original is just plain wrong with current drives.

    > As to how they fly, take off from a CSS landing zone is mechanically straightforward, although a lot of research has
    > gone into minimizing wear during that process.


    Waffle. It certainly doesnt take weeks.

    > Loading unloaded heads is usually done by a static ramp that feeds the head in close to the correct level to minimise
    > the approach distance. The mechanics of the situation require the slider to briefly kiss the disk on approach,


    Like hell it does.

    > even if the manufacturers do not mention it,


    They dont because it doesnt happen.

    > simply because the unloaded detent position has to be many microns from the surface to ensure separation. The ramp
    > can't know where the disk actually is to the necessary degree of accuracy,


    The ramp is to retract the heads from the media so they no longer land on it anymore.

    > and ground-effect can't give you the gees to decelerate the approach speed in time.


    Have fun explaining how real planes land.

    > http://www.hitachigst.com/tech/techlib.nsf/techdocs/9076679E3EE4003E86256FAB005825FB/$file/LoadUnload_white_paper_FINAL.pdf


    That actually says that those drive DONT land the head on the platter when the drive stops, what I said.

    And it does NOT say that the head touch the platter when they start flying either.
     
    Rod Speed, Jun 21, 2009
    #13
  14. GreenXenon

    Guest

    GreenXenon <> wrote:

    >I notice with ZIP discs and floppies, the disc is a soft dark-brown
    >round film-like material that can easily be shredded -- with paper-
    >shredder -- to remove confidential information.


    >However, the magnetic platters in HDDs are much harder and metallic.


    >Why don't they make the hard-disc-drive platters soft like the discs
    >of floppies and ZIPs? It would be so much easier to remove unwanted
    >confidential information then. Simply unscrew the HDD, remove the soft
    >platters and dump them into a paper-shreder.



    A Major Difference between HDDs and Floppy Diskettes
    ( Or: Usually there's no need to worry about Magnets near an HDD)
    http://mirror.href.com/thestarman/asm/mbr/DiskTerms.htm

    Here's something I found of interest (same link):
    "The platters of a common hard drive are not completely sealed off
    from the outside as many people think. Therefore, you can damage an
    HDD by running it at too high of an altitude where there is less air
    pressure; since the heads may stay in contact with the platters or
    skip up and down!" (the same force is involved or lacking due to air
    pressure)

    --

    unfortunate ad placement, Mc Donalds
    http://img95.imageshack.us/img95/4426/unfortunateadplacement.jpg
     
    , Jun 21, 2009
    #14
  15. GreenXenon

    Rod Speed Guest

    Tim Jackson wrote
    > Rod Speed wrote
    >> Tim Jackson wrote
    >>> Rod Speed wrote
    >>>> Tim Jackson wrote


    >>>>> When I worked in the business and learned about the "kissing track" where the head hits the disk in order to find
    >>>>> it,


    >>>> That was never the case with PC hard drives.


    >>>>> or lands on it when it stops,


    >>>> That doesnt happen anymore either.


    >>>>> I did the calculation of how long it would take the head to reach
    >>>>> flying height if it approached slow enough that ground effect
    >>>>> would stop it before it hit, I forget the answer now but it was
    >>>>> huge, at least weeks.


    >>>> Have fun explaining how hard drive heads fly then.


    >>> AFAIK both Contact Stop/Start (CSS) and Loading/Unloading are still in use on PC drives.


    >> The heads are loaded and unloaded but they do not land on the platter anymore.


    >> There was never ever any 'kissing track'. What we did see with stepper motor head actuator drives was the heads moved
    >> against a physical
    >> stop to recalibrate, but thats not a particular TRACK on the drive.


    > Whatever you like to call it. It has nothing to do with head
    > calibration, it's the zone of the disk under the ramp where the heads approach the disk and establish a stable flying
    > height.


    Wrong. There was no ramp initially, that came later to avoid
    stiction which happens due to the very smooth platter and head
    and the heads never ever deliberately contact the platter anymore,
    because the heads dont get anywhere hear the platter from the
    ramp until the platters are up to rotation speed and so the last
    thing you want is a head crash. They certainly dont ever
    deliberately 'the head hits the disk in order to find it'.

    That is utterly garbling what actually happens even with the original PC drives.

    >>> Certainly both have been used on PCs,


    >> Nope, particularly that original claim about a TRACK.


    >>> with load/unload now being back in fashion,


    >> Load and unload is an entirely separate matter to the heads
    >> landing on the platters when the drive stops spinning. That
    >> doesnt happen anymore, tho it did certainly happen at one
    >> time. Thats what stiction is, the heads stuck to the platter.


    >>> and I am not aware of any "third way".


    >> There is in the sense that the heads are retracted from the platters at shutdown.


    > That is load/unload.


    Yes, but the heads never deliberately contact the
    platter when there is a load/unload ramp in use.

    >>> If you have an alternative answer please share it,


    >> I did, I told you that the first never happened, and
    >> that heads no longer land on the platters anymore.


    > That's not an alternative explanation, it's just a denial.


    You're lying now.

    > If I'm out of date, I'm happy to learn.


    You clearly arent. You just try to bullshit your way out of your predicament instead.

    > I admit it was the 1970's when I worked in computer design, but I do try to keep up.


    You need to try much harder.

    > But telling me it's no longer done like that, it's now done by magic, doesn't help.


    I never ever said its dont by magic, liar. That cite you posted clearly states how the
    load/unload ramp works and why the heads no longer contact the platters anymore.

    > I trained as a physicist: I need mechanisms,


    That cite you post has the mechanisms, read it again.

    > and numbers that add up.


    Then you will have to find those for yourself.

    You dont need the numbers anyway when the heads only leave the
    load/unload ramp when the platter is up to speed and the heads just
    fly because the platter is up to speed when the head comes off the ramp.

    >>> just denigrating my answer does not help anyone.


    >> It does point out that your original is just plain wrong with current drives.


    > Not until you tell us how they get to descend from unload height to
    > flying height without touching the disk.


    That cite you posted does that, by waiting for the platters to come
    up to speed before the heads are moved off the ramp over the platters.

    >>> As to how they fly, take off from a CSS landing zone is
    >>> mechanically straightforward, although a lot of research has gone into minimizing wear during that process.


    >> Waffle. It certainly doesnt take weeks.


    > Do the sums yourself then.


    No thanks. Its obvious to anyone with a clue that if the platters
    are up to speed before the heads come off the ramp, they will
    fly when they are designed to fly over the platters.

    > How long does it take to get from say .001" down to flying height, slow enough that ground effect stops you hitting
    > the disk.


    Not even a second.

    >>> Loading unloaded heads is usually done by a static ramp that feeds
    >>> the head in close to the correct level to minimise the approach
    >>> distance. The mechanics of the situation require the slider to
    >>> briefly kiss the disk on approach, simply because the unloaded
    >>> detent position has to be many microns from the surface to ensure
    >>> separation. The ramp can't know where the disk actually is to the
    >>> necessary degree of accuracy,


    >> The ramp is to retract the heads from the media so they no longer land on it anymore.


    > Sure. And when they come back off the ramp... ? How high above flying height are they? How fast are they descending?
    > How much time do they have to stop in?


    Find that for yourself.

    > How far *below* flying height must they get in order to obtain a decelerative force to stop the descent in that time?


    You dont know that they do ever get below flying height.

    > Go do the maths.


    No need, whoever designed them did that and it clearly works fine.

    >>> ground-effect can't give you the gees to decelerate the approach speed in time.


    >> Have fun explaining how real planes land.


    > They use observation and/or instruments to predict the approach to the ground and reduce their descent rate.


    Wrong again. With light aircraft that have a significant ground effect, you
    can close your eyes and use the ground effect to reduce the descent rate.

    And dont try claiming it doesnt work like that, I've done it.

    > If they don't know their relative altitude they are rarely successful at landing on one piece.


    Wrong, as always. Some like the F111 are effectively driven into the ground
    and the undercarraige absorbs the remaining descent force. They dont flare.

    Same thing happens with aircraft carriers, landing is more of a controlled
    crash than anything else, there is no flare at all, essentially because there
    isnt enough deck with an aircraft carrier and the last thing you want is flare.

    > And they don't fly at 1.5mm either, they fall many times that distance on landing.


    > Planes cannot land by ground effect alone.


    Wrong, as always.

    > It would require an impractically shallow angle of approach even to get to a flare height of metres, never mind
    > millimetres.


    Utterly mangled all over again. You just flare and use ground effect then.

    > And planes do touch the ground, they don't go to level ground-effect flight.


    You can if you want to, and some have been designed to do that, usually over water.

    > I have yet to see a disk slider with elevator flaps, although maybe one day...


    Flaps are there to increase the rate of descent and to change the attitude
    when descending so you can see better. No need for them on hard drive heads.

    And there is no such animal as 'elevator flaps' on a plane anyway.

    >>> http://www.hitachigst.com/tech/techlib.nsf/techdocs/9076679E3EE4003E86256FAB005825FB/$file/LoadUnload_white_paper_FINAL.pdf


    >> That actually says that those drive DONT land the head on the platter when the drive stops, what I said.


    >> And it does NOT say that the head touch the platter when they start flying either.


    > It says they all did until about 1995,


    It ACTUALLY says that the START on the platter when the platter isnt rotating, a different thing entirely.

    > which is over a decade of PCs, and contradicts what you said.


    Like hell it is.

    > I agree it doesn't discuss the mechanism of approach to flying height, I did say that.


    And you mangled it completely.
     
    Rod Speed, Jun 21, 2009
    #15
  16. GreenXenon

    Guest

    "Rod Speed" <> wrote:

    >> Whatever you like to call it. It has nothing to do with head
    >> calibration, it's the zone of the disk under the ramp where the heads approach the disk and establish a stable flying
    >> height.

    >
    >Wrong. There was no ramp initially, that came later to avoid
    >stiction which happens due to the very smooth platter and head


    No, it was the glue (used to keep the magnetic media on the aluminum
    platters), would get sticky when hot, when the heads parked
    themselves, the glue would cool down and the heads would become stuck.
    Mostly a Seagate problem.

    >and the heads never ever deliberately contact the platter anymore,
    >because the heads dont get anywhere hear the platter from the
    >ramp until the platters are up to rotation speed and so the last
    >thing you want is a head crash. They certainly dont ever
    >deliberately 'the head hits the disk in order to find it'.


    You should take the cover off a hard drive and watch how the heads
    operate, you turn off the HD the heads move very quickly to the inner
    sector, where they sit, as the heads need air to float or lift
    themselves up - can't remember the effect that causes this - but it
    was used on those old 8" floppies (in plastic cases).

    The floppies would sag at the outside edge, and this effect would
    bring the edges up and the floppy even. (No, not centrifugal force)

    I've never seen a ramp, when I take a HD apart it's always the same
    the heads are as close to the spindle as they can get, and all the
    heads are sitting on the platters.

    --

    Amazing Street Basketball Tricks
    http://www.youtube.com/v/fYlTrl6Cwwc
     
    , Jun 21, 2009
    #16
  17. GreenXenon

    Rod Speed Guest

    wrote
    > Rod Speed <> wrote


    >>> Whatever you like to call it. It has nothing to do with head
    >>> calibration, it's the zone of the disk under the ramp where the
    >>> heads approach the disk and establish a stable flying height.


    >> Wrong. There was no ramp initially, that came later to avoid
    >> stiction which happens due to the very smooth platter and head


    > No, it was the glue (used to keep the magnetic media on the aluminum
    > platters), would get sticky when hot, when the heads parked themselves,
    > the glue would cool down and the heads would become stuck.


    Utterly mangled all over again. There was never any 'glue
    (used to keep the magnetic media on the aluminum platters)'

    > Mostly a Seagate problem.


    >> and the heads never ever deliberately contact the platter anymore,
    >> because the heads dont get anywhere hear the platter from the
    >> ramp until the platters are up to rotation speed and so the last
    >> thing you want is a head crash. They certainly dont ever
    >> deliberately 'the head hits the disk in order to find it'.


    > You should take the cover off a hard drive and watch how the heads operate,


    You should with a modern drive.

    > you turn off the HD the heads move very quickly to the inner sector,


    Not anymore.

    > where they sit, as the heads need air to float or lift themselves up


    The heads actually fly.

    > - can't remember the effect that causes this


    The heads are flying.

    > - but it was used on those old 8" floppies (in plastic cases).


    Wrong again. 8" floppys were not in plastic cases,
    they were just bigger versions of 51/4" floppy.
    http://en.wikipedia.org/wiki/File:Floppy_disk_2009_G1.jpg

    > The floppies would sag at the outside edge, and this
    > effect would bring the edges up and the floppy even.


    Utterly mangled all over again. they were just bigger versions of 51/4" floppys.

    > (No, not centrifugal force)


    They just rotate inside the jacket, just like 51/4" floppys do.

    > I've never seen a ramp,


    You need to try a modern drive.

    > when I take a HD apart it's always the same the heads are as close to
    > the spindle as they can get, and all the heads are sitting on the platters.


    You need to try a modern drive.
     
    Rod Speed, Jun 22, 2009
    #17
  18. GreenXenon

    Guest

    "Rod Speed" <> wrote:

    >>> Wrong. There was no ramp initially, that came later to avoid
    >>> stiction which happens due to the very smooth platter and head


    >> No, it was the glue (used to keep the magnetic media on the aluminum
    >> platters), would get sticky when hot, when the heads parked themselves,
    >> the glue would cool down and the heads would become stuck.


    >Utterly mangled all over again. There was never any 'glue
    >(used to keep the magnetic media on the aluminum platters)


    I had read and been informed that it was the glue, apparently it was
    due to "lubricants used to coat the platters"
    http://en.wikipedia.org/wiki/Stiction#Hard_disk_drives

    And you are right about the Ramps they are addressed in the link as
    well - I do need to open up a new HD, but don't have a bad one; lot's
    of old drives, less than 2gigs mostly
    --

    Amazing Street Basketball Tricks
    http://www.youtube.com/v/fYlTrl6Cwwc
     
    , Jun 22, 2009
    #18
  19. GreenXenon

    Rod Speed Guest

    wrote
    > Rod Speed <> wrote
    >> wrote
    >>> Rod Speed <> wrote


    >>>> Wrong. There was no ramp initially, that came later to avoid
    >>>> stiction which happens due to the very smooth platter and head


    >>> No, it was the glue (used to keep the magnetic media on the aluminum
    >>> platters), would get sticky when hot, when the heads parked themselves,
    >>> the glue would cool down and the heads would become stuck.


    >> Utterly mangled all over again. There was never any 'glue
    >> (used to keep the magnetic media on the aluminum platters)


    > I had read and been informed that it was the glue,


    And you're so stupid that you cant work out what is mindless silly shit and what isnt.

    > apparently it was due to "lubricants used to coat the platters"
    > http://en.wikipedia.org/wiki/Stiction#Hard_disk_drives


    Yep, for when the heads did land on the platters. They dont anymore.

    > And you are right about the Ramps they are addressed in
    > the link as well - I do need to open up a new HD, but don't
    > have a bad one; lot's of old drives, less than 2gigs mostly


    Yeah, tho the newest of those may well have the ramps.

    No point tho, wikepedia is right on that and you can find plenty of
    documentation on them from the hard drive manufacturers too like
    http://www.hitachigst.com/tech/techlib.nsf/techdocs/9076679E3EE4003E86256FAB005825FB/$file/LoadUnload_white_paper_FINAL.pdf
     
    Rod Speed, Jun 22, 2009
    #19
  20. GreenXenon

    Guest

    "Rod Speed" <> wrote:

    >> I had read and been informed that it was the glue,


    >And you cant work out what is mindless silly shit and what isnt.


    Nope, it was the answer for years on stiction, I am one of many who
    accepted that.
    --

    Amazing Street Basketball Tricks
    http://www.youtube.com/v/fYlTrl6Cwwc
     
    , Jun 22, 2009
    #20
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