[TUHS] Disk data layout (was: /dev/drum)

Paul Winalski paul.winalski at gmail.com
Sat Apr 28 04:16:31 AEST 2018

On 4/27/18, Dave Horsfall <dave at horsfall.org> wrote:
> On Wed, 25 Apr 2018, Paul Winalski wrote:
>> Bin number was zero except on the IBM 2321 data cell drive.  CKD drives
>> supported a variable number of records on each track, hence the term
>> "record" rather than "sector".
> Would that have been the infamous chicken-plucker?[*]  Wherein if things
> went OK, then they were OK, but if things went wrong...

That's the one.  I'd always heard "noodle picker", though.  From the
outside it looked like a drum in the shape of a multi-sided polygon.
Each bin held a number of wide pieces of multitrack magnetic tape.  To
seek to your data, the drum rotated under a head that pulled the
appropriate tape out of the bin and wrapped it on rotating drum.  From
there reading and writing was much like any other drum device.  It's
as if someone asked Rube Goldberg to design a disk drive.

-Paul W.

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