Le 05/01/2016 16:29, Rainer Weikusat a écrit :
Didier Kryn<[email protected]> 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'.
Good find Rainer. But I don't fully understand what you mean by:
Keep the stuff needed by everyone (and the swap space) on the fast disk
and use the slower one for 'individual users files'.
Do you mean the applications in /usr/bin aren't used by everyone?
Or they don't deserve to be launched quickly? For me the only reason why
they were not on the small fast disk is that this disk was full, ant it
was full because it was small. Therefore, maybe Rob Landley is giving
wrong details (or he refers to a later setup), but the reason he gives
for the split makes full sense.
I'm not denying that the necessity, or an advantage, of a split has
persisted for decades. On the contrary, I find it interesting to know
that this necessity showed up at the very begining.
The split is a complication; and a complication should only exist
for a good reason. Therefore I think it is a sane attitude to question
this good reason.
Didier
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