Re: ReiserFS, two oddities

["Norman Diamond" <ndiamond@wta.att.ne.jp>]

Andries Brouwer replied to me:

> > This is tangential to my observations about bad blocks (which the disk's
> > firmware refused to reallocate during reads, writes, and S.M.A.R.T. long
> > self-tests).  I have had two odd observations which seem related to
> > ReiserFS on perfectly good blocks.
> >
> > Here is partial output from fdisk's p command, copied by hand:
> >   /dev/hda8   18169578  29431079   5630751   83  Linux
> >
> > The sector is readable if I ignore partitions:
> >   # dd if=/dev/hda of=/dev/null bs=512 skip=29431074 count=1
> >   1+0 records in
> >   1+0 records out
> > but not if I address it from inside the partition:
> >   # dd if=/dev/hda8 of=/dev/null bs=512 skip=11261496 count=1
> >   dd: reading `/dev/hda8': Input/output error
> >   0+0 records in
> >   0+0 records out
> >
> > LBA sector number 29431074 is inside the partition.  18169578 + 11261496
> > = 29431074, verified several times.  11261496 / 2 = 5630748, verified
> > only twice, but it is within the quantity of 1K Linux blocks that the
> > partition has.  Why is the sector unreadable when read from inside the
> > partition?
>
> If I understand you correctly, there may never have been a bad block.
> That is good for Toshiba, no reason to say bad things about their disks.

Dream on.  LBA sector number 29431074 might or might not be near LBA sector
number 19021882, but 19021882 was indeed bad.  I already posted the filename
of the file which used to contain that block (it took about two days of
"find"ing and "cp"ing to /dev/null to find which file it was), and already
posted several of my dd's of the LBA sector number in the non-partitioned
device /dev/hda.  Dr. Brouwer, you know quite a lot about disks, how could
you possibly pick on the situation with sector 29431074 and pretend that
this explains the ton of observations about sector 19021882?

> Also, if there was no bad block, then no reallocation is needed.

Hey, I've received about 30 spams today trying to sell the kind of drugs
that you seem to have taken today.

By the way, after sector 19021882 was reallocated, the S.M.A.R.T log showed
that the number of reallocations had increased from 3 to 4.  And further
reads had no more failures and no more reallocations after that one finally
took place.  So the drive even disagrees with you, although it took ages and
an unknown amount of experiments to get it there.

Dr. Brouwer, I know that you know more about disk drives than you pretend to
in this message.  Please try to avoid spreading misinformation.

> You show that dd reads this sector without problems.
> But you see an I/O error when it is just at the edge of the partition.
> That I/O error may well be generated by Linux, not by the disk.

Yes, this one was, as explained by Oleg Drokin because of the 4K cluster
size in ReiserFS.  This is still unrelated to the genuinely bad block.

> [didnt you get error messages in dmesg?]

I get so many boot errors about other things that scroll off the screen
without getting into dmesg, sometimes I wonder why I still bother testing.
Meanwhile, dmesg has a few comments from ReiserFS about properly
initializing itself with respect to partitions, but no boot-time errors in
ReiserFS.