Re: fuzzy disks, Is Parallel Programming Hard, And, If So, What Can You Do About It?

On 5/26/2025 10:42 AM, John Levine wrote:

According to Chris M. Thomasson <chris.m.thomasson.1@gmail.com>:

For some damn reason I thought of a fractal disk arm, an arm that had a
fractal structure, the disk rotates, but the fractal arm can read from
many places at once? Try not to flame me too much. ;^)

 Dunno about fractal, but I have used head per track disks with a fixed arm
with many heads, and a disk with a crooked Y-shaped arm with two heads over
two tracks.

Yup.  And IIRC the IBM 3380 had a linear actuator with two heads per arm, one covering the outer cylinders, the other the inner cylinders. The tradeoff was shorter seeks, thus smaller seek time but higher cost due to more heads.

None of them could do more than one transfer at a time but I
think that was a limit of the electronics of the era, not a fundamental
issue.

Depends on what you mean by more than one transfer at a time.  If you mean two simultaneous independent data streams to the host, that would require a second host connection.  But if you mean two simultaneous transfers into a buffer in order to get higher host transfer rate, that is apparently now available.
https://www.seagate.com/innovation/multi-actuator-hard-drives/
However, I think that, except for streaming applications, the bigger payoff is two simultaneous seeks.
--
  - Stephen Fuld
(e-mail address disguised to prevent spam)