Re: Filesystems

[Anne & Lynn Wheeler <lynn@garlic.com>]

Peter Flass <peter_flass@yahoo.com> writes:
> [not topposted due to user request]
> AIX has had a "journaled file system" (JFS) for years, and I'd have to
> assume they weren't the first.  It has recently been ported to OS/2.

i believe it may have been the first unix product filesystem. it was
originally done using the rios (aka power/6000) "database memory"
.... basically segment that had fine-grain modification turned on. the
filesystem metadata was mapped into the segment. at checkpoints
... could go around and find all the areas that had been modified and
log them (note that logs tends to be cyclical and overwrites after
things have been commited, journals tend to be long term archives of
changes).

as part of being able to have it run on other hardware, palo alto did
a more conventional version where explicit calls were made to log as
changed happened. it turned out that the explicit calls were less
overhead than running around afterwards and finding all the modified
data. this was all before the AIXV3 with JFS actually shipped. Note
that palo alto had also done AOS (bsd) for the PC/RT as an alternative
to the AIXV2 (at&t) shipped from austin.

-- 
Anne & Lynn Wheeler | http://www.garlic.com/~lynn/ 
Internet trivia 20th anv http://www.garlic.com/~lynn/rfcietff.htm