[TUHS] The evolution of Unix facilities and architecture

[imp@bsdimp.com (Warner Losh)]

On Fri, May 12, 2017 at 9:52 AM, Chet Ramey <chet.ramey at case.edu> wrote:
> On 5/12/17 10:30 AM, Larry McVoy wrote:
>> On Fri, May 12, 2017 at 02:56:59PM +0100, Tim Bradshaw wrote:
>>> When I found out about this I thought seriously of shorting Sun's
>>> stock (if I knew how to do that).  I would have made money.  As it was
>>> we stuck with logged UFS which, by 2007 or so was seriously bulletproof.
>>
>> Wait, someone added logging to UFS?  Is there a writeup of that anywhere?
>
> You could look at the soft updates paper from 1999 for Kirk's perspective.
>
> https://www.usenix.org/legacy/event/usenix99/full_papers/mckusick/mckusick.pdf
>
> There was a paper about journaled soft updates, too:
>
> https://www.mckusick.com/softdep/suj.pdf

There's also Margo's paper on LFS, which added logging to UFS, though
by the time it was over it wasn't recognizable.

https://www.usenix.org/publications/library/proceedings/sd93/seltzer.pdf

The Journaled updates, though, is that someone added an intent log to
UFS + SoftUpdates. This was used to replay the last few operations
when doing fsck coming back up after a crash. There's also something
called gjournal, which adds a different type of journaling to UFS, but
the less said about that train-wreck the better.

Warner