On Sun, Jan 25, 2004 at 12:25:16PM +1100, [EMAIL PROTECTED] ([EMAIL PROTECTED]) wrote:
> On 25 Jan, Jobst Schmalenbach wrote:
> >
> > all,
> >
> > I have a problem getting data of a tape, dd reports errors,
> > but yes I want *that* data (this is the only one).
> >
> > Now I read something of dd using "conv=noerrors", but I
> > also read that this ONLY works if st can handle this.
>
> Have you tried that, then, or do you mean it's not supported? I've
> certainly used the option successfully with failing floppies.
I was wondering whether the "st" driver supports taht option.
>
> > I do not need the data where the error occurs but later within
[snip]
> dd if=/dev/amandatape of=/backup/OUT_02.tgz bs=32k conv=noerror
> didn't help?
>
It failed once. This time I added conv=noerror,notrunc cause the problem
is that gzip is then getting the wrong data.
> > So if I would now go to block 805 or even futher and then
> > pad the missing blocks with some data.
> >
> >
> > * Can I do this?
> > * What data would that need to be?
> > * Are there any other ways to pull that data of?
>
> I don't know a way to do that. And I think there's a fundamental
> problem with writing a single compressed file to any backup device:
> AFAIK, if there is any data corruption at some point in the compressed
> data stream, there's no way to "re-sync" to recover data beyond that
> point.
There is two different types of compression
* hardware
* software
AFAIK you cannot recover from software compressed data but you can
from hardware compressed data ....
> There may be commercial ventures who have ways to recover data from the
> tape, just as there are for disc drives. Others here may know more.
>
> Sorry I couldn't be more help.
thanks for trying ..
jobst
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