18 Mar
2016
18 Mar
'16
8:13 a.m.
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
filesystem.
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...
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt(a)softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
18 Mar
18 Mar
8:36 a.m.
New subject: Early non-Unix filesystems?
On Thu, Mar 17, 2016 at 7:13 PM, Johnny Billquist <bqt(a)update.uu.se> wrote:
On 2016-03-18 03:00, Warren Toomey
<wkt(a)tuhs.org> wrote:
It did do something really interesting tho; segments could have multiple
names.
Given a segment "foo", you could "add_name foo bar". "foo"
and "bar" now
refer to the same segment, much like a UNIX link. However, if you move the
segment to another directory, the names follow -- they are part of the
segment metadata, not entries in the segment's directory.
This was leveraged by the binder; when binding an executable segment with
multiple entry points, the binder will add the entry points to the names of
the segment, and the shell would select the correct entry point based on
the name.
bound_dir_cmds_
list
rename
delete
You can use 'bound_dir_cmds_$list' or 'list'.
-- Charles
I would think that something like Multics had
something similar, but I
have no idea about that one...
Mutlics doesn't separate the name and the data.
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