[TUHS] Boston Children's Museum RK05 Driver: Questions

[Warren Toomey via TUHS]

Hi all, for some reason I thought about the RK05 driver written by
Bill Mayhew and Brent Byer at the Boston Children's Museum. Based
on the minor device number, it remaps blocks 1 to 2435 as blocks
2436 to 4871, and remaps blocks 2436 to 4871 down to blocks 1 to 2435.

According to the notes in the driver (see dmr/rk.c in
https://www.tuhs.org/Archive/Distributions/UNSW/1/record0.tar.gz):

  The effect of this mapping is to centralize disk head motion about the
  center of the disk. The optimization is ideal for those RK's which
  serve as both root device and swap device. It is less than ideal,
  although probably still an improvement over traditional form, for RK's
  used exclusively as mounted file systems.

Question: how much of a win was this, and why was the idea of moving
(some/all) of the i-nodes to the centre of the disk not used until
we got the fast filesystem?

Cheers, Warren