Date: Thu, 22 Jul 2004 19:03:18 +0200 From: Johan Pettersson <manlix@demonized.net> To: Scott Long <scottl@samsco.org> Cc: cvs-src@freebsd.org Subject: Re: cvs commit: src/sys/kern kern_shutdown.c Message-ID: <20040722190318.5fe349d3.manlix@demonized.net> In-Reply-To: <40FFC4CD.4080706@samsco.org> References: <200407212045.i6LKjHvX090599@palm.tree.com> <40FEE569.2010209@elischer.org> <40FEE6CA.3090005@samsco.org> <20040722092441.GH3001@cirb503493.alcatel.com.au> <40FFC4CD.4080706@samsco.org>
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On Thu, 22 Jul 2004 07:44:45 -0600 Scott Long <scottl@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?
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