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    SubjectRe: sector size of 2068?
    On Thu, 27 Aug 1998, Brandon S. Allbery KF8NH wrote:
    > | optimization to select the proper head, etc. Therefore I doubt
    > | that the "real" block-size is 2068. In practice, it's usually
    > | 512 or a multiple thereof.
    > +--->8
    > It has been suggested that they chose a format that makes the disk look as
    > big as possible. That it's not *usable* in that format (to my knowledge, no
    > other OS does 2068-byte sectors either) isn't significant to marketroids
    > pushed to "demonstrate" their numbers....

    It's unlikely that the report from SCSI `read capacity` command is
    correct. The firmware in most drives that I've seen maintain a
    "bitmap" that tells the hardware what head to use. Essentially
    when you run out of the bits representing a read or write in progress,
    you automatically pick up the next head via a simple hardware decode.

    This won't work with sector lengths that are not powers-of-two.
    Spiral disks (for video, etc.) make extensive use of bitmap control.

    So I think that the 2068 really means "this drive has not been formatted".
    Your point about disk size is noted. It would be nice to find out if
    the drive really has its stated capacity (after it is formatted). I
    think you will be pleasantly surprised. Most SCSI drives have LOTS
    of spare sectors which are marked spare so the drive capacity is
    artificially reduced to the published capacity during the format.

    Bad sectors are transparently re-mapped during use so SCSI drives
    should never have any "bad sectors". If they occur, it's time to
    back up everything and low-level format it again.

    Dick Johnson
    Penguin : Linux version 2.1.118 on an i586 machine (66.15 BogoMips).
    Warning : It's hard to remain at the trailing edge of technology.

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