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    SubjectRe: sector size of 2068?
    On Thu, 27 Aug 1998, Brandon S. Allbery KF8NH wrote:

    > In message <>,
    > "Richard B. Johnson" writes:
    > +-----
    > | On Mon, 24 Aug 1998, Peter wrote:
    > | > What would need to be changed to make a SCSI disk with sector_size
    > | > reporting back as 2068 work?
    > |
    > | In the SCSI controller BIOS setup, low-level format the drive using
    > | your new controller. The drive was apparently low-level formatted on
    > +--->8
    > We've been through that already. His question is, why can't we use it with
    > 2068? (The reason he asked being that more space is "wasted" with 512-byte
    > sectors due to sector mark overhead.)

    Not really, but its nice to think someone believes I'd come up with
    something like that. The reason I asked was because its on a sparcstation
    and there's no low-level format, and thus is unusable.

    Asside from that, the answer was to put together a 486 and have adaptec's
    controller have fun with it. Works fine, but i'm a little bit perplexed
    as to its result. It being a "9.1 Gig scsi drive". The drive is a
    ST410800W in case you're wondering, and the full details are at

    What interests me about the resulting behavior is what fdisk says:
    Device Flag Begin Start End Blocks Id System
    /dev/sdb1 0 0 4923 8839246+ 83 Linux native
    /dev/sdb3 0 0 4923 8839246+ 5 Whole disk

    Is 8.43 gig really how much is left when you partition off a 9.09 gig
    drive? That just doesn't seem sane. Somebody tell me if I'm crazy.

    > The short answer is that most of the kernel assumes that disk sector sizes
    > are a power of 2 and therefore can be represented via bit shifting 2068
    > isn't a power of 2, so isn't eligible. 2048 might well be doable, though,
    > if you really wanted it....
    > | 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....

    This sounds reasonable, and probably very likely.

    -- Peter

    "What is a magician but a practicing theorist?"
    -- Kenobi

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