Re: About USB hard drives and errors

On 20100410_092044, Clive McBarton wrote:
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Paul E Condon wrote:>
dumpe2fs -b <device> is supposed to print the bad blocks that have
been marked on a device. When I run it, it prints nothing. I find it
hard to believe that a 500GB HD contains ZERO bad blocks.

Every HD that is even remotely close to being usable will always have
zero bad blocks when seen from outside the HD. All HDs have error
recognition and error correction and automatic replacement of faulty
sectors with spare ones. A HD will only show bad blocks after all of its
remapping area is used, at which point it is far beyond being usable.

In other words, scanning for bad blocks on a HD cannot work.

Thanks Clive. Your post has been invaluable in fixing some faulty thinking
on my part, and in provoking other useful posts. But I want more ...

The errors that I am experiencing are all similar. The first
indication of a problem is a message from the kernel (I think). An
example is:

kernel: [78454.939948] journal commit I/O error

This appears on all xterm windows on the affected machine. On the
xterm that is controlling a process that is using one of the USB
drives, there follows a long sequence of error messages about the
drive being read-only, which stops after a while. Or sometimes I stop
it by typing ^C on that xterm.

When this happens, all the USB drives (3 of them) disappear from
/dev/disks/by-label (they are all labeled by me). I have not
discovered any to make them re-appear, short of rebooting the
computer. After reboot, I run e2fsck on all of them, and always get a
longish delay on each while e2fsck commits (or whatever) the
journal. This can take a few seconds or up to half a minute. Then
I manually mount them using pmount, and all data upto the point
where the crash happened seems to be present.

I have installed smartmontools, but I think there is some
incompatibility between the installed version and the installed
docs. The README.Debian makes reference to editing some lines in the
config file that are not present in the default, package installed,
config file. There is (apparently) some incompatibility between using
the daemon and using smartctl. The problem host is running Lenny, but
the docs seem to be the same as on a different host that is running
Squeeze.

I would very much appreciate some help in understanding the docs.
What is a safe thing for a nubie to type as a first command to
smartctl?

--
Paul E Condon
pecondon@xxxxxxxxxxxxxxxx


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