cvs commit: src/sys/kern kern_shutdown.c

[Johan Pettersson]

On Thu, 22 Jul 2004 07:44:45 -0600
Scott Long <scottl at samsco.org> wrote:

> Peter Jeremy wrote:
> > On Wed, 2004-Jul-21 15:57:30 -0600, Scott Long wrote:
> > 
> >>Implementing a journalling filesystem would be a much more
> >beneficial>use of time here.
> > 
> > 
> > You still wind up with unwritten data in RAM, just less of it.
> > 
> > How much effort would be required to add journalling to UFS or UFS2?
> > How big a gain does journalling give you over soft-updates?
> > 
> 
> That's a very good question.  A group at RPI has been working on it
> for some time, but I'm not sure how close they are to having it done. 
> If you look in the commercial world, Apple, Sun, and Wasabi/NetBSD
> have all done it successfully (Wasabi's isn't open source, btw).  My
> guess is that it would take about 4-5 months to get it going, and then
> at least 8-12 months to ensure that there are no bugs and to tune
> performance. Certainly not impossible, but not something that would be
> production quality on short notice.  I think that you would also have
> to make it othogonal to softupdates.
> 
> The gain that you get is that your filesystem recovery time drops
> tremendously.   You also have a much better chance of all of the
> metadata being on the disk and recoverable.  Furthermore, it opens the
> door for data+metadata journalling for even more protection (at a
> large cost to speed and/or buffer-cache pressure, of course).
> 
> Scott

Isn't there ongoing work to port XFS to FreeBSD?