Re: ext3-2.4-0.9.4

Alan Cox
2001-07-26T13:52:33Z

> On Thu, 26 Jul 2001, Rik van Riel wrote:
> > In fact, knowing how hard disks work mechanically, only
> > journaling filesystems could have an extention to make
> > this work. Ie. this is NOT something you can rely on ;)
>
> This is not about failing hard disks. It is about premature
> acknowledgment of something which has not happened at that time.

Rik is right. It isnt just about premature notification - its about
atomicity. At the point you are notified the data has been queued for disk
I/O. Even on traditional BSD ufs with synchronous metadata you still had
points where a crash left the rename partially complete and nothing but a
log or an atomic update system is going to fix that.

> The competition is there and it has names: BSD + ufs + softupdates,
> Solaris + logging ufs. Read MTA mailing lists before obstructing.

All of which are - not unsuprisingly - using a log. In fact Solaris logging
ufs and ext3 are very similar ideas - adding a log to an existing fs.

Alan