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

[Paul Winalski via TUHS]

On Sat, Jan 31, 2026 at 9:01 PM Warren Toomey via TUHS <tuhs at tuhs.org>
wrote:

>
> 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?
>
> It was not uncommon to have unconventional data placement schemes on disk
files to minimize head movement.  IBM's compilers used something called
split cylinder allocation for their compilers' three scratch files.
Instead of having a contiguous set of cylinders for each file, each
cylinder was split between the three scratch files (for example, file #1
using heads 1-3, file #2 heads 5-7, etc.).  This allowed the compiler to
use the three files simultaneously with little or no head movement.

I imagine that by the time the fast filesystem came along memory was cheap
and plentiful enough to allow sufficient caching (both in the disk
controller and by the driver) to mitigate most head motion delays for
frequently accessed data structures such as inodes.

-Paul W.