Date: Fri, 19 Aug 2011 21:39:17 -0400 From: Dan Langille <dan@langille.org> To: Jeremy Chadwick <freebsd@jdc.parodius.com> Cc: freebsd-stable@freebsd.org Subject: Re: bad sector in gmirror HDD Message-ID: <B6B0AD0F-A74C-4F2C-88B0-101443D7831A@langille.org> In-Reply-To: <20110819232125.GA4965@icarus.home.lan> References: <1B4FC0D8-60E6-49DA-BC52-688052C4DA51@langille.org> <20110819232125.GA4965@icarus.home.lan>
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On Aug 19, 2011, at 7:21 PM, Jeremy Chadwick wrote: > On Fri, Aug 19, 2011 at 04:50:01PM -0400, Dan Langille wrote: >> System in question: FreeBSD 8.2-STABLE #3: Thu Mar 3 04:52:04 GMT 2011 >> >> After a recent power failure, I'm seeing this in my logs: >> >> Aug 19 20:36:34 bast smartd[1575]: Device: /dev/ad2, 2 Currently unreadable (pending) sectors > > I doubt this is related to a power failure. > >> Searching on that error message, I was led to believe that identifying the bad sector and >> running dd to read it would cause the HDD to reallocate that bad block. >> >> http://smartmontools.sourceforge.net/badblockhowto.html > > This is incorrect (meaning you've misunderstood what's written there). > > Unreadable LBAs can be a result of the LBA being actually bad (as in > uncorrectable), or the LBA being marked "suspect". In either case the > LBA will return an I/O error when read. > > If the LBAs are marked "suspect", the drive will perform re-analysis of > the LBA (to determine if the LBA can be read and the data re-mapped, or > if it cannot then the LBA is marked uncorrectable) when you **write** to > the LBA. > > The above smartd output doesn't tell me much. Providing actual SMART > attribute data (smartctl -a) for the drive would help. The brand of the > drive, the firmware version, and the model all matter -- every drive > behaves a little differently. Information such as this? http://beta.freebsddiary.org/smart-fixing-bad-sector.php -- Dan Langille - http://langille.org
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