I don't believe I explained myself properly. Most backup applications will
skip a bad block (or even several blocks) of data and continue the restore.
What I describe arises when the corruption exceeds the ability of the
software to recover from errors. In that case, an entire file (or several if
not the whole tape depending on the location of the error) will be rendered
unrecoverable. The validation of the archive/backup at the time only ensures
the initial process succeded. The problematic variable is between archival
and retrieval. With digital audio recordings, such errors will only render
that portion of the recording unrecoverable.
As for error correction, that is a function of the format (AIT/LTO/DLT/etc)
and software used for backup/archival. On 'trusting' a datatape to be
readable 25-30 years from now; I completely agree. That is the figure I
recall being used when discussing longevity. In my case, I re-archive
critical material every three years. Data on tape IMO is far too susceptible
to corruption to be relied upon for a longer timeframe than that.
> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:[log in to unmask]] On Behalf Of John Spencer
> Sent: Thursday, June 09, 2005 2:47 PM
> To: [log in to unmask]
> Subject: Re: [ARSCLIST] Longevity of data tape?--
> This is an incorrect statement. There are various backup
> applications that will skip a bad block of data and continue
> the restore process, as well as applications that will report
> on the quality of the data archive as it is being written.
> Error correction is not a function of the data storage tape itself.
> And I would never trust a data storage tape to be readable
> 25-30 years from now.
> John Spencer
> On Jun 9, 2005, at 2:36 PM, Jeffrey Kane wrote:
> > I've seen the figure 25-30 years bandied about for data tape. Data
> > backups are a double edge sword. They have better error
> correction so
> > the data is more resilient. However, if there's an
> unrecoverable error
> > it renders ALL data for that particular file (and if it's in the
> > directory area, all data on the tape) unrecoverable. With digital
> > audio tape the error only affects that portion of the recording.