Didier Kryn <kryn@???> writes:
> Le 02/01/2016 03:44, Stephanie Daugherty a écrit :
>> Regardless of who proposed it, merged /usr is still a reckless change
> that needlessly complicates things.
>
>

>     Hey Stephanie.

>

>     The simple fact of splitting executables between two different
> directories *is* a complication; merging them back would be a
> *simplification* :-). I've read, from a guy who followed the story,
> that it was originally split because the first disk was too
> small.

Quoting something Rob Landley (who has certainly no more experience with
stuff that happened in the first half of the 1970s than I do and possibly
less) wrote as gospel is not such a good idea. There's a paper by Dennis
Richtie, "The UNIX Time-Sharing System" published in 1974 (AFAICT, it's
not on Landley's "list of computer history sources" list) which states

    The PDP-11 has a 1M byte fixed-head disk, used for file system
    storage and swapping, four moving-head disk drives which each
    provide 2.5M bytes on removable disk cartridges, and a single
    moving-head disk drive which uses removable 40M byte disk packs.

        [...]

    In our installation, for example, the root directory resides
    on the fixed-head disk, and the large disk drive, which con-
    tains user's files, is mounted by the system initialization
    program

And considering this, the "ran ouf of space and mindlessly duplicated
all the stuff onto a new disk" hypothesis is at least questionable when
considering this as the 'fixed head disk' was a small, expensive,
'high-performance' storage device and the moving head disk a large,
cheap and slow one. Which suggests functional reasons for the split:
Keep the stuff needed by everyone (and the swap space) on the fast disk
and use the slower one for 'individual users files'.