Date: Sat, 15 May 2004 23:41:41 -0300 (ADT) From: "Marc G. Fournier" <scrappy@hub.org> To: Michael Hamburg <hamburg@fas.harvard.edu> Cc: freebsd-current@freebsd.org Subject: Re: fsck in -current Message-ID: <20040515233728.Q30269@ganymede.hub.org> In-Reply-To: <D3AE316C-A6D9-11D8-89DA-0003939A19AA@fas.harvard.edu> References: <20040515220258.H920@ganymede.hub.org> <D3AE316C-A6D9-11D8-89DA-0003939A19AA@fas.harvard.edu>
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On Sat, 15 May 2004, Michael Hamburg wrote: > On May 15, 2004, at 9:08 PM, Marc G. Fournier wrote: > > > > > I'm seriously considering putting 5.x onto my next server, to take > > advantage of, if nothing else, the reduction in the GIANT LOCK reliance > > ... one "concern" I have is how fsck works in 5.x ... > > > > Right now, on 4.x, I have an fsck running that has been going for ~3hrs > > now: > > > > # date; ps aux | grep fsck > > Sat May 15 22:04:00 ADT 2004 > > root 40 99.0 4.5 185756 185796 p0 R+ 6:55PM 164:01.60 fsck -y > > /dev/da0s1h > > > > and is in Phase 4 ... > > > > In 5.x, if I'm not mistaken, fsck's are backgrounded on reboot, so that > > the system comes up faster ... but: > > > > a. wouldn't that slow down the fsck itself, since all the processes on > > the > > machine would be using CPU/memory? > > Yes. You can probably renice it or something, though, and it wouldn't > take that much longer. > > Furthermore, if I recall correctly, it doesn't check as much after a > crash when soft-updates are enabled. See below. > > > b. how long could fsck run in the background safely ... like, if I > > rebooted a machine, fsck backgrounded and then all the processes > > started up, is there a risk involved? > > > > No, fsck should be able to run in the background indefinitely with > basically no risk, so long as you have free space on your disk. The > way that the latest fsck works is that it snapshots the drive, and then > checks the snapshot; the only type of error that it's expecting to find > is files which have been deleted but whose space has not been > reclaimed. This space can be recovered without confusing running > processes. 'k ... fsck just started spewing messages to the screen, which is nice cause now I know its actually doing something: ZERO LENGTH DIR I=5159669 OWNER=root MODE=40755 SIZE=0 MTIME=May 10 17:32 2004 CLEAR? yes now, the ZERO LENGTH DIR is a result of using unionfs ... but would that cause any issues with the snapshotting? like, how much 'free space' would you need, and what happens ifyou don't have enough? :( ---- Marc G. Fournier Hub.Org Networking Services (http://www.hub.org) Email: scrappy@hub.org Yahoo!: yscrappy ICQ: 7615664
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