Date: Thu, 22 Jul 2004 11:07:54 -0600 From: Scott Long <scottl@freebsd.org> To: Nate Lawson <nate@root.org> Cc: cvs-src@freebsd.org Subject: Re: cvs commit: src/sys/kern kern_shutdown.c Message-ID: <40FFF46A.2080703@freebsd.org> In-Reply-To: <40FFEB86.2050209@root.org> References: <200407212045.i6LKjHvX090599@palm.tree.com> <40FEE569.2010209@elischer.org> <40FEE6CA.3090005@samsco.org> <20040722092441.GH3001@cirb503493.alcatel.com.au> <40FFEB86.2050209@root.org>
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Nate Lawson 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? > > > Kirk pointed out something to me the other day which many people don't > think about. None of the journaling systems has had its recovery mode > fully tested, especially on very large systems (dozen TB). It turns out > that memory pressure from per-allocation unit state is a big problem > when you are trying to recover a huge volume. > > Just because it says "journaling" doesn't make it good. > You are very correct that there are issues like this, and that's why I said that it would take a while to chase out the bugs and make it production quality. However, given the enterprise nature of Sun, I'd say it's a bit of a stretch to think that they haven't tested their f/s on multi-terabyte arrays. Even Apple advertises multi-terabyte storage with their XServe, so I'd be surprised if they hadn't done at least some testing there. Scott
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