how good is the data reliability with CD ROM and DVD RAM?

Alexander Schreiber als at
Mon Jul 23 10:51:59 CDT 2018

On Sun, Jul 22, 2018 at 08:06:24PM +0200, Carlo Pisani via cctalk wrote:
> thus DDS4, LTO2, DLT: which is the best tape?

If you even remotely care about your data, stay far away from DDS.
In a previous job we used DDS3 tapes as system backup and restore
tapes (since the machines could boot from them). Those were written
at most once a month and in 1.5 years there I accumulated a nice stack
of 'dead' (hard read errors) tapes. I think none survived more than
half a dozen write cycles and they got read not much more.

Generally, avoiding any helical scan tape technology (DDS, AIT) is
probably a good idea on account of increased head & tape wear this

Personally, I have good experience with both DLT and LTO, both are
linear scan technologies and IIRC are specified to last at least
1-2 decades given proper storage.

Of course, you still want several generations and copies of your backups.

Another thing to keep in mind: it is nice if your backup medium lasts
decades, but what about the reader for it? Will that be available
down the road as well and usable?

And, not to forget: what format are your backups written in. Something
standard like POSIX tar or some proprietary format used by some
commercial software, which might have availability issues in the

Kind regards,

> 2018-07-22 18:11 GMT+02:00 Jon Elson via cctalk <cctalk at>:
> > On 07/22/2018 10:52 AM, Chuck Guzis via cctalk wrote:
> >>
> >> On 07/22/2018 06:33 AM, Paul Koning via cctalk wrote:
> >>>
> >>>
> >>>> On Jul 21, 2018, at 3:25 PM, Carlo Pisani via cctalk
> >>>> <cctalk at> wrote:
> >>>>
> >>>> ...
> >>>> and what about magnetic-tapes? (e.g. DDS4, DLT, LTO2)
> >>>>
> >>>> which of them lasts for the most?
> >>>
> >>> I don't know specifically.  I do know that plain old audio tapes may fail
> >>> -- I have perhaps 100 cassettes recorded in the 1970s.  Most of them are
> >>> fine, but essentially all of them that are Fuji brand have failed utterly.
> >>
> >> Half-inch open-reel tape at 1600 PE density.  Should be good for 50
> >> years at least.
> >>
> >>
> > Well, you are one of the experts in this, but it all depends on storage
> > conditions.  Also, the extended-length tapes were too thin, and suffered
> > from creasing and print-through.  Badly stored, and you can kiss your data
> > goodbye in less than 5 years.
> >
> > Jon

"Opportunity is missed by most people because it is dressed in overalls and
 looks like work."                                      -- Thomas A. Edison

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