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Re: backup archive format saved to disk

Douglas Tutty wrote:
On Tue, Dec 05, 2006 at 07:55:40PM -0600, Mike McCarty wrote:

Douglas Tutty wrote:

On Tue, Dec 05, 2006 at 06:57:38PM -0600, Ron Johnson wrote:


I'm not complaining Mike.  Also, note who's saying what; there's a few
voices in this conversation.

Sorry, did I miss an attribution? If so, then I apologize.

Please don't take my questions the wrong way.
I am very gratefull for the wisdom.  I'm just trying to tease apart
where failures can occur and what can mitigate them.

Fair enough. See my other message which describes hypothetical
data recovery on a damaged set of CDROMs.

I guess I don't know what the question is.

Since I don't __know__ that it can, I'm assuming that it can't.  I'm
playing my own devils advocate and trying to find out how to plan to be
able to read successfully off a drive with bad blocks after years of
sitting on a shelf.

IF this is what your goal is, then, as I pointed out, you can implement
your own FEC.

Yes I could.  The origional question was to see if one existed already.

Yes, FEC is used on all modern technology data storage that I know of,
with the possible exception of CDROMs. I haven't studied the low level
data storage format they use to know whether they use any FEC when
storing data as opposed to music. I know the music format uses nested
Reed-Solomon codes. For all I know, the ISO format has FEC embedded
in it as part of the FS, though I doubt it.

I'm focusing on the one-drive issue because this is one drive sitting in
a bank vault.  This is __archive__ (just like tape).  I have backup
procedures as a separate issue.  One of the places that backup data goes
to is the bank vault archive.

If the issue is a drive, then you need more than one drive. If the
drive itself fails, then you are SOL.

So drive failures are atomic?  I.e. if in 5 years I go to read a drive

If in X years you plug the drive into your machine, and smoke
pours out, you are going to have difficulty reading any medium
you may put into it. You are banking on the format of the tape
or whatever not changing in that time. If the format becomes
obsolete, and your drive fails, then you are SOL.


Hmm. You going to become an expert at designing ECC? I suggest you take
a course in abstract algebra first.

Can (or at least I used to be able to) do the algebra, but that's not
the issue.  There are programs like par2 that do the ECC stuff but put
it in separate files.  If I went that route, I just have to pack it all

I don't understand that. It shouldn't matter where the correction bits
get stored, so long as the number of bits that get damaged is less than
what the code can correct.

This message made from 100% recycled bits.
You have found the bank of Larn.
I can explain it for you, but I can't understand it for you.
I speak only for myself, and I am unanimous in that!

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