[TUHS] Quick Question: Early Filesystems and Name/Metadata Separation?

[Dan Cross via TUHS]

On Tue, Sep 16, 2025 at 4:44 AM Noel Chiappa via TUHS <tuhs at tuhs.org> wrote:
>     > From: Dan Cross
>
>     > I wondered if perhaps Multics had the concept
>
> You have no idea of the depth of the tarpit you just stepped into! Making it
> even deeper, Multics has two quite different generations of file systems;
> read about the second one (reasons why, etc) here:
>
>    https://www.multicians.org/nss.html
>
> File metadata was kept in the directory in the first; in the second, much
> metadata _was_ moved to a thing called a 'Volume Table of Contents' (VTOC),
> which is sort of like the ilist (the above says "[w]e were aware of the Unix
> file system design, where there was a similar split between naming data in
> directories and physical data in the inode"). However, even in the New
> Storage System, _some_ metadata (ACLs, etc) remained in the directories, see:
>
>   https://www.multicians.org/mtbs/MTB-220.pdf
>
> Just to increase the complexity, in both systems, in addition to the
> segment's primary name (sort of a 'hard link'), and logical ('soft') links,
> segments could have additional secondary names (much used for short names for
> commands - the familiar ls, cp, mv, etc were all short names), kept in the
> same directory as the primary name:
>
>   https://multicians.org/mga.html#additionalnames
>
> (Please excuse Bernie.) Are we having fun yet? :-)

Ooops, yup: I had looked at the VTOC code in Multics, but sent before
I finished editing my reply to mention it beyond a half-finished
sentence; mea culpa, there!  FWIW from what I saw, the VTOC entry
contains physical disk addresses for files, and is indexed by a "VTOCE
index", which is an integer that is stored in branch directory
entries.  However, most of the metadata about the file, such as
timestamps, ACL pointers, the primary name, size, etc remains in
branch entries.

For those interested in the gory details, the definition of a Multics
directory entry, as of MR12.8 is online:
https://dps8m.gitlab.io/sb/MR12.8/library_dir_dir/include/dir_entry.incl.pl1.html

(No problem about Bernie; he's a character.)

>     > it appears that the Berkeley Timesharing System for the SDS-930 may
>     > have had something like hard links
>
> I was wondering if BTSS (on which, of course, Ken worked) had such, but was
> too lazy to look. Thanks!

Sure thing!

        - Dan C.