Date: Tue, 19 Jul 2005 20:01:50 -0700 (PDT) From: Don Lewis <truckman@FreeBSD.org> To: davidt@yadt.co.uk Cc: freebsd-stable@FreeBSD.org Subject: Re: dangerous situation with shutdown process Message-ID: <200507200301.j6K31oX8042414@gw.catspoiler.org> In-Reply-To: <20050716133710.GA71580@outcold.yadt.co.uk>
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On 16 Jul, David Taylor wrote: > On Sat, 16 Jul 2005, Matthias Buelow wrote: >> David Taylor <davidt@yadt.co.uk> writes: >> >> >> A corrupted journal can be detected. If it's corrupted, discard >> >> the whole thing, or only the relevant entry. The filesystem will >> >> remain consistent. >> >> If track corruption occurs after the journal is written, it doesn't >> >> matter, since at boot the journal will be replayed and all operations >> >> will be performed once more. >> > >> >The track which is corrupted could contain data that wasn't written >> >to in months. How would the journal help? >> >> I don't understand this question. > > When the drive is powered off, the track being written to at that point > may be corrupted, right? That track may contain sectors that the OS > did't change. These sectors would not be mentioned in the journal. > How would a journaling fs fix the corruption? > > I suppose this could be avoided by requiring that all writes (and > journal entries) somehow correspond to a full track. (Which I suppose > they may do already, but I don't think so). The track size is not constant. There are more sectors in the outer cylinder tracks than there are in inner cylinder tracks. I'm not even sure if it is possible to extract the detailed geometry info from the drive.
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