Date: Mon, 15 Dec 2008 21:08:05 +0100
From: Folkert van Heusden <folkert@vanheusden.com>
To: Pavel Machek <pavel@suse.cz>
Cc: Theodore Tso <tytso@mit.edu>, Chris Friesen <cfriesen@nortel.com>,
       mikulas@artax.karlin.mff.cuni.cz, clock@atrey.karlin.mff.cuni.cz,
       kernel list <linux-kernel@vger.kernel.org>, aviro@redhat.com
Subject: Re: writing file to disk: not as easy as it looks
Message-ID: <20081215200805.GI7083@vanheusden.com>
References: <20081202094059.GA2585@elf.ucw.cz> <20081202140439.GF16172@mit.edu> <20081202152618.GA1646@ucw.cz> <20081202163720.GB18162@mit.edu> <49356EF2.7060806@nortel.com> <20081202205558.GD20858@mit.edu> <20081215110310.GA10274@elf.ucw.cz>
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> > There are certainly things you can do.  Put your fileservers's on
> > UPS's.  Use RAID.  Make backups.   Do all three.  :-)
> 
> Okay, so we pretty much	know that ext3 journalling helps in "user hit
> the reset button" case. (And we are pretty sure ext2/ext3 works in
> "clean unmount" case). Otherwise
> 
> *) kernel bug -> journalling does not help.
> 
> *) sudden powerfail -> journalling helps works on SGI high-end
> hardware. It may or may not help on PC-class hardware.
> 
> We already do periodic checks, even on ext3. Maybe we should do fsck
> more often if we see evidence of unclean shutdowns (because we know
> PC hardware is crap...).

What we might need is on-line fsck. E.g. fsck while the fs is still
mounted.

Might be tricky to implement.


Folkert van Heusden

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