Date: Tue, 5 Sep 1995 15:41:33 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: peter@taronga.com (Peter da Silva) Cc: terry@lambert.org, peter@taronga.com, hackers@FreeBSD.ORG Subject: Re: Bad superblock? Message-ID: <199509052241.PAA24452@phaeton.artisoft.com> In-Reply-To: <199509052102.QAA22315@bonkers.taronga.com> from "Peter da Silva" at Sep 5, 95 04:02:53 pm
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> > If the answer could be "controller failure" than the reason it doesn't > > update the backup superblocks should be obvious. > > Doesn't "sync" update the backup superblock anyway? yes, but not the clean bit. Consider a failure and a loss of the original superblock; to be consistent, the backup superblock must force a fsck. This all boils down to an issue of media perfection and the fact that a sector failure can take out critical data at all; or in the particular case that started this thread, the MSDOSFS can be of by two bytes and blow your superblock. Trying to optimize for the case of a particular know failure is a bogus exercise. Either fix the failure or live with the existing recovery; the existing recovery takes a lot more failure modes than the MSDOSFS crap into account, and losing them because a similar but not identical failure has occured (and is thus not recoverable) is a Bad Thing(tm). If this isn't your issue, then you don't have an issue; your superblock is good, use it instead of trying to play with a backup. 8-). Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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