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Date:      Wed, 12 May 2010 09:16:09 +0200
From:      Alexander Best <alexbestms@uni-muenster.de>
To:        ticso@cicely.de
Cc:        freebsd-current@freebsd.org
Subject:   Re: fsck unable to read disk sectors
Message-ID:  <AANLkTinNsP_2fo62WrdpuIVqTuziwS44v6CBPbcUKdTx@mail.gmail.com>
In-Reply-To: <20100512014651.GN73283@cicely7.cicely.de>
References:  <permail-20100329221104f0889e8400006cd5-a_best01@message-id.uni-muenster.de> <3a142e751003291708nc3e110bjca1789cc807f61a2@mail.gmail.com> <AANLkTikKgJQ5iEHm8Zl45eAZY2ppsYYCkmXivVj89tXk@mail.gmail.com> <AANLkTim0zpd3iVHu-O6Zo8w_h8mtrLPdsrw9qDP0jKZM@mail.gmail.com> <20100512014651.GN73283@cicely7.cicely.de>

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On Wed, May 12, 2010 at 3:46 AM, Bernd Walter <ticso@cicely7.cicely.de> wro=
te:
> On Tue, May 11, 2010 at 10:15:13PM +0200, Alexander Best wrote:
>> i've posted a log here which is pretty self explanatory:
>>
>> http://pastebin.com/tn3NiDDW
>>
>> On Tue, May 11, 2010 at 10:13 PM, Alexander Best
>> <alexbestms@uni-muenster.de> wrote:
>> > the problem is getting more awkward.
>> >
>> > if i do `fsck /dev/label/rootfs` fsck complains that it cannot read a
>> > specific sector of my hdd as i mentioned before. if i run fsck on the
>> > device node directly using `fsck /dev/ada0p3` however, fsck succeeds.
>
> So this is not hardware it is bad partitioning.

puh. that's a relief. but since smartd didn't complain about anything
and dd if=3D/dev/ada0 of=3D/dev/null bs=3D1m reported no errors i kinda
thought that my hdd wasn't the cause for this.
>
>> > what i did was to boot into single user mode with / being mounted read
>> > only. for some reason however fsck will check /dev/label/rootfs in
>> > write mode, but if i want fsck to check ada0p3 it will only do so in
>> > read mode.
>> >
>> > this looks like something is really broken. right now the only way to
>> > get the clean flag set on my hdd is to boot from a livefs cd and then
>> > run `fsck /dev/ada0p3` (again: `fsck /dev/label/rootfs` will NOT
>> > succeed).
>
> One of the typical problems users have is that they forget that
> adding a label takes one sector, so the labeled device is smaller.
> This is no problem if you create the filesystem on the labeled
> drive, but often enough people add the label after creating the
> filesystem.
> Everything seems to work fine until the FS decides to use that special
> sector.
> I wouldn't add a label for ufs anyway, since UFS has labeling itself,
> which is also handled by glabel module and doesn't require extra space.
> Just setup the ufs label with tunefs -L and use the resulting /dev/ufs/..=
.
> device.
> You only need extra label for swap, but this is not problem, since
> it has no persistent ondisk structures.

thanks a lot for the explanation. i never would have thought about
that. since / already has a ufs label i'll simply change fstab to use
/dev/ufs/rootfs as /, then boot into single user mode and remove the
glabel for ada0p3. i followed the steps described in the gpart(8)
manual to create my partition layout. maybe the manual should state
that if one wants to create a glabel it should happen before creating
a filesystem?

>
>> > this is the output of `glabel status` btw:
>> >
>> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 Name =A0Status =A0Components
>> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 label/boot=
 =A0 =A0 N/A =A0ada0p1
>> > gptid/e52df583-e446-11de-bb92-000fb58207c8 =A0 =A0 N/A =A0ada0p1
>> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 label/swap=
 =A0 =A0 N/A =A0ada0p2
>> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 label/rootfs =
=A0 =A0 N/A =A0ada0p3
>> >
>> > cheers.
>> >
>> > On Tue, Mar 30, 2010 at 2:08 AM, Paul B Mahol <onemda@gmail.com> wrote=
:
>> >> On 3/29/10, Alexander Best <alexbestms@wwu.de> wrote:
>> >>> hi there,
>> >>>
>> >>> when doing fsck on my / fs i get this error:
>> >>>
>> >>> "Cannot Read BLK. 471617640" and "The Following Disk Sectors could n=
ot be
>> >>> read: 471617643". after this message the partition gets marked dirty=
.
>> >>>
>> >>> i performed the following steps to verify the problem:
>> >>>
>> >>> 1) dd if=3D/dev/ada0 of=3D/dev/null bs=3D1m
>> >>> 2) fsck / under freebsd 7
>> >>> 3) mount -u -o snapshot /.snap/snapshot1 / && fsck_ffs /.snap/snapsh=
ot1
>> >>>
>> >>> all three steps showed no problem with that harddrive whatsoever. al=
so
>> >>> smartd
>> >>> doesn't complain about anything.
>> >>>
>> >>> i'm running HEAD (r205860) on amd64.
>> >>>
>> >>> this is the output of `dmesg -a|grep ada0`:
>> >>>
>> >>> ada0 at ahcich2 bus 0 scbus3 target 0 lun 0
>> >>> ada0: <SAMSUNG SP2504C VT100-50> ATA-7 SATA 2.x device
>> >>> ada0: 300.000MB/s transfers (SATA 2.x, UDMA6, PIO 8192bytes)
>> >>> ada0: Command Queueing enabled
>> >>> ada0: 238474MB (488395055 512 byte sectors: 16H 63S/T 16383C)
>> >>
>> >> Last time I tried ahci on dead disk it did not complained at all
>> >> (usually I get dead LBA listed on console).
>
> --
> B.Walter <bernd@bwct.de> http://www.bwct.de
> Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
>



--=20
Alexander Best



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