Date: Wed, 12 Feb 2003 23:00:45 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: Michael Sierchio <kudzu@tenebras.com> Cc: Darren Pilgrim <dmp@pantherdragon.org>, freebsd-questions@FreeBSD.ORG, freebsd-fs@FreeBSD.ORG Subject: Re: Why is there no JFS? Message-ID: <3E4B429D.5DCFB0E9@mindspring.com> References: <3E4A5B77.5080103@ant.uni-bremen.de> <3E4A863E.2030801@potentialtech.com> <3E4A8EF5.1070308@ant.uni-bremen.de> <3E4A9712.8030609@potentialtech.com> <3E4AA331.5040701@ant.uni-bremen.de> <3E4AA734.5040102@potentialtech.com> <045401c2d2db$f9d45c30$0a0aa8c0@dweebsoft.com> <20030212225631.GA10375@HAL9000.homeunix.com> <005801c2d2eb$aa5fae60$1200a8c0@gsicomp.on.ca> <3E4ADDDE.5040208@pantherdragon.org> <3E4B138F.26E32E75@mindspring.com> <3E4B2433.70301@pantherdragon.org> <3E4B27E6.6010501@tenebras.com>
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Michael Sierchio wrote: > Darren Pilgrim wrote: > >> Soft updates are disable on / by default because of the chicken > >> and egg problem of runing tunefs on /. > > > > If that's the problem, then why doesn't sysinstall enable it by default > > when partitioning for a new install? > > You can certainly change the options in sysinstall to force Softupdates > on / > > In general, there's little to be gained from it -- on most systems, / is > essentially a read-only filesystem, with very little metadata changed except > for atime. > > BTW, IIRC you can certainly 'tunefs -n enable /' while in single-user mode. If it's mounted read-only, which requires no other mounts, then you can do it. I believe the reason it's not "on" in sysinstall is that sysinstall tries to mount things async on the initial install, so that doing things like unpacking ports doesn't take forever. If it fails, you can just restart, and having to do that a couple of times is still faster than waiting for ordered metadata. The technical reason that it doesn't do it is that the mount update is not logically an "unmount without destroying vnodes(inodes) in core, with a remount with the new options". The main reason for that is that the dependencies go all the way to the buffer cache, and the backing vnode (e.g. the "raw" device) that's mounted does not necessarily get its buffers flushed. Basically, you'd have to put a little more work into the "mount update" code. This was discussed a long time ago on -arch, when soft updates first came into FreeBSD, and then again every 18 months or so, ever after. See Kirk's postings on the subject, if you don't want to take mine for it. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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