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Re: checking for bad media

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Sat, 30 Oct 2004 23:52:06 -0700 (PDT)

:>    Maybe it's the hard disk you are installing to that is having the 
:>    media problems instead of the CD.  That's the only thing I can think
:>    of that would result in an error at the same place every time.  Usually
:>    IDE driver problems, bad cables, and bad CD drives error out in a
:>    different location each time.
:The errors are with the cd device reads. I'm kinda stuck as far as
:capturing the output, the installer won't work via ssh (with su or ssh
:-l installer), stops near beginning, during setup. And I had bought
:null modem cables to try a serial install, but all the forknibbler docs
:(which I need) are unavailable atm, even by google cache...

    Hmm.  Very odd.  If you have another CD drive (of a different brand)
    that you can throw in there it might be worth trying that.  You can
    also try forcing the driver to talk to the CD more slowly using
    atacontrol.  e.g. login as root on the CD and do:

    [ list current ATA modes ]
    atacontrol mode 0
    atacontrol mode 1

    If the CD is on channel 1 and has negotiated PIO4 you could try forcing
    it to operate more slowly with something like :

    atacontrol mode 1 PIO3 -

    Then login again as the installer and see if it gets further.

:>    When a modern HD goes bad the only real solution is to buy a new one.
:>    It might be possible to salvage it by running the manufacturer's low
:>    level formatting tool for the drive, assuming one is available.  (This
:>    also means you'd probably have to load up windoz in order to run the
:>    tool).
:I wasn't looking to "get away with" a bad disk (via badsect), I just want
:to verify some disks are good, or bad as the case may be, before I build
:on them.
:// George
:George Georgalis, systems architect, administrator Linux BSD IXOYE

    If the disk isn't known to be bad and you just want to check
    that it's still probably good I would just use 'dd' to read
    the the raw device and see if it has any problems, and run an
    iostat in another window to monitor the progress.  If the disk
    has to retry a sector the transfer rate will drop dramatically
    for a few seconds.

    window#1: dd if=/dev/ad0 of=/dev/null bs=128k
    window#2: iostat ad0 1

					Matthew Dillon 

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