[GRLUG] Mounting DVDs

[Bob Kline]

Re optical media decays, yes, this is
always a possibility.  Bad batch of blanks?
There's a vast lore about what causes
CDs and DVDs to deteriorate.  Whether
rewriteable media are better or worse
than write once, etc.

But there is still the issue of the original
machine being able to read them.  Perhaps
that has to do with alignment issues between
DVD units.  One hates to think about this,
but apparently it is common enough.
It somewhat says one should keep around
the very DVD unit they used to make the
backups.

But better is to try them right after making
them, one another unit if possible, which I
suspect few of us usually do.....

Thanks for the tip about ddrescue.  I'll
take a look at it.  The media in question
have no scratches, but there are other
possibilities.  In the end I'll probably
just put the DVDs in to the old unit, read
them, move them to the new unit, and
consider it yet one more lesson learned.

Your point about several kinds of backup
is well taken.  It's all a matter of how much
what you are backing up is worth to you.
And of course one always has to ask
whether their backup devices are working
as expected...

    -- Bob




On Thu, Jan 21, 2010 at 11:16 AM, Michael Mol <mikemol at gmail.com> wrote:

> On 1/21/2010 10:43 AM, Bob Kline wrote:
> > mount /dev/dvd
> >
> > That would be fine if it worked...
> >
> > On occasion I'll see "no medium found
> > on /dev/sr0," the dvd unit.  Other times
> > I might see "can't read superblock," or
> > something thereabouts.  I gather that
> > indicates that the file system type is not
> > correctly determined.  But if I specify it,
> > that should not be an issue.
> >
> > Suggestions?  Marginal DVD unit?
>
> mount -t auto /dev/srN /mountpoint
>
> ddrescue will help you recover data from scratched discs.  Optical media
> decays, though, so it's possible it may be totally unrecoverable. (Some
> brands and dye types decay faster than others. I used to know a lot
> about which were more reliable, but that's all pretty much slipped away.
> For backup purposes, don't trust just one backup medium, and keep burned
> discs in dark places.)
>
> Another means of backing up optical media is to use cdrdao, and rip in
> disc-at-once mode. I had to resort to that to back up an old Playstation
> disc. You should then be able to use cdrdao to burn it on to new media.
> I haven't dug into how to directly access the resulting .bin file, yet.
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