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.
Jeff
-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx] On Behalf Of John Spencer
Sent: Thursday, June 09, 2005 2:47 PM
To: ARSCLIST@xxxxxxxxxxxx
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
John Spencer
www.bridgemediasolutions.com
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.