Re: fsck unable to read disk sectors

On Wed, May 12, 2010 at 3:46 AM, Bernd Walter <ticso_at_cicely7.cicely.de> wrote:
> 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_at_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=/dev/ada0 of=/dev/null bs=1m 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:
>> >
>> >                                     Name  Status  Components
>> >                               label/boot     N/A  ada0p1
>> > gptid/e52df583-e446-11de-bb92-000fb58207c8     N/A  ada0p1
>> >                               label/swap     N/A  ada0p2
>> >                             label/rootfs     N/A  ada0p3
>> >
>> > cheers.
>> >
>> > On Tue, Mar 30, 2010 at 2:08 AM, Paul B Mahol <onemda_at_gmail.com> wrote:
>> >> On 3/29/10, Alexander Best <alexbestms_at_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 not be
>> >>> read: 471617643". after this message the partition gets marked dirty.
>> >>>
>> >>> i performed the following steps to verify the problem:
>> >>>
>> >>> 1) dd if=/dev/ada0 of=/dev/null bs=1m
>> >>> 2) fsck / under freebsd 7
>> >>> 3) mount -u -o snapshot /.snap/snapshot1 / && fsck_ffs /.snap/snapshot1
>> >>>
>> >>> all three steps showed no problem with that harddrive whatsoever. also
>> >>> 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_at_bwct.de> http://www.bwct.de
> Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
>



-- 
Alexander Best