On 2016-03-18 03:00, Warren Toomey <wkt(a)tuhs.org> wrote:
It's a bit off-topic, but what were non-Unix
filesystems like around 1969-1970?
The PDP-7 filesystem has i-nodes (file metadata) and filenames separate
from the i-nodes. This allows hard links and thus a non-tree structured
This has always struck me to be one of the most important features of
the Unix filesystem: names separated from the rest of the file metadata,
and arbitrary hard links so that there is no preferred filename.
Were these features in other contemporaneous filesystems?
I don't know exactly how contemporary ODS-1 is. It's the file system
used on RSX-11, and I think it should atleast trace back to around 1972,
but I can't say more for sure.
Anyway, ODS-1, just like the Unix file system, have the directory hold
just the filename and a file identifier (pretty much the same as inode
number). There are of course some differences in details, but I would
say it is very similar to how Unix works. ODS-1 do not have reference
counting, but instead allows dangling directory entries that do not
point to valid files. Instead ODS-1 have a generation counter for each
file identifier, so that when it is reused, links to the old file will
not accidentally refer to the new file.
I would think that something like Multics had something similar, but I
have no idea about that one...
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