Date: Thu, 13 Feb 2003 13:11:23 -0800 From: David Schultz <dschultz@uclink.Berkeley.EDU> To: Darren Pilgrim <dmp@pantherdragon.org> Cc: Terry Lambert <tlambert2@mindspring.com>, Brooks Davis <brooks@one-eyed-alien.net>, Matthew Emmerton <matt@gsicomp.on.ca>, Daxbert <daxbert_news@dweebsoft.com>, Bill Moran <wmoran@potentialtech.com>, Heinrich Rebehn <rebehn@ant.uni-bremen.de>, freebsd-questions@FreeBSD.ORG, freebsd-fs@FreeBSD.ORG Subject: Re: Why is there no JFS? Message-ID: <20030213211123.GA15047@HAL9000.homeunix.com> In-Reply-To: <3E4BFE74.2000103@pantherdragon.org> References: <005801c2d2eb$aa5fae60$1200a8c0@gsicomp.on.ca> <3E4ADDDE.5040208@pantherdragon.org> <3E4B138F.26E32E75@mindspring.com> <20030212210721.A9481@Odin.AC.HMC.Edu> <20030213051952.GA11572@HAL9000.homeunix.com> <3E4B467B.4DCF6D5@mindspring.com> <20030213074449.GA12084@HAL9000.homeunix.com> <3E4BA1D2.E259308@mindspring.com> <20030213191356.GA14560@HAL9000.homeunix.com> <3E4BFE74.2000103@pantherdragon.org>
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Thus spake Darren Pilgrim <dmp@pantherdragon.org>: > David Schultz wrote: > >Thus spake Terry Lambert <tlambert2@mindspring.com>: > >>IMO, this is not the reason for them being off on /; the real > >>reason is as I've stated: sysinstall expects the common case to > >>be an initial install, not operations after the initial install, > >>and so does not turn it on by default. > > > > > >The original reason was due to the possibility of installworld > >failing, due to the case described above not being handled > >particularly well in FreeBSD 4.X. Sysinstall is perfectly happy > >with creating a root FS with softupdates enabled. If someone > >wants to bother changing the default for what little difference it > >might make in installworld/installkernel times, I would support it. > > For what its worth, I think all that's needed is to change line 339 in > usr.sbin/sysinstall/label.c: ... > I think softupdates is still (viewed as) riskier than synchronous > writes, at least for large numbers of writes (like installworld) to a > filesystem of limited size, so someone is going to inevitably ask if > FreeBSD should be loading the bullets as well. Personally, if it's a > matter of choosing overall safety or a performance gain for something > you really shouldn't be doing to a live machine anyway, I'll take the > safe route and option the performance gain. I've heard that argument, and while I think it has *some* validity in general, I don't buy it for installworld/installkernel in particular. Softupdates guarantees metadata consistency (modulo hardware issues that have been discussed on this list before), but it can reorder writes and delay the amount of time it takes your data to hit the disk. For an installworld, this means that the window during which you have a partially installed world is slightly larger, but installworld takes a while, so the window is already pretty darn big. The whole rationale for doing installworld/installkernel in a particular sequence is that with any luck, you can boot to single-user mode after something goes wrong and finish the job (or revert to the old kernel.) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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