Date: Thu, 22 Jul 2004 10:26:07 -0700 From: Nate Lawson <nate@root.org> To: Scott Long <scottl@freebsd.org> Cc: cvs-src@freebsd.org Subject: Re: cvs commit: src/sys/kern kern_shutdown.c Message-ID: <40FFF8AF.5090805@root.org> In-Reply-To: <40FFF46A.2080703@freebsd.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> <40FFF46A.2080703@freebsd.org>
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Scott Long wrote: > Nate Lawson wrote: >> Peter Jeremy wrote: >>> 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. I was referring to the herd of Linux journaling systems. > Even Apple advertises multi-terabyte > storage with their XServe, so I'd be surprised if they hadn't done at > least some testing there. > 2 TB? -- -Nate
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