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

[Alexander Schreiber]

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
causes.

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
future.


Kind regards,
            Alex.

> 
> 2018-07-22 18:11 GMT+02:00 Jon Elson via cctalk <cctalk at classiccmp.org>:
> > 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 classiccmp.org> 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

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