Freebsd filesystem ( hard reboot )
peter.schuller at infidyne.com
Thu Dec 6 11:20:15 PST 2007
> Well any number of things, but the most recent was a prolonged power
It is important to differentiate between expected fsck activity and
If you are running without write caching turned on (which is the default), a
power outtage will constitute a crash from which a file system cannot
guarantee to recover unless it takes measure to punch through the write cache
at appropriate moments.
If you machine shutdown softly as a result of the UPS communicating that power
was running out, you "should" not have to fsck (barring other issues in the
past). fsck need in these cases would indicate a software bug, or a hardware
If on the other hand your machine just lost power when the UPS finally died,
you are relying on luck for recovery if you're on ufs/reiserfs/xfs/etc. Some
environments will correctly handle this (e.g., ZFS), but most won't. The
problem being that drive write caching will prevent the file system from
guaranteeing ordering of certain critical operations that must be ordered in
order to guarantee successfull recovery to a consistent state.
That said, you are not supposed to need to answer interactive questions on
boot for all cases of expected inconsistencies. If you are getting prompts as
a result of unexpected inconsistencies, that indicates *something* is wrong.
/ Peter Schuller
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