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Re: How to verify newly burned disc


i wrote:
> > > where they [ASUS] expect us to still find M-Disc DVD+R media.

Michael Lange wrote:
> > 10 4.7 GB discs at 85.11 € + 7.31 € for shipping from Japan :-)
> > Australia, 5 discs for "~" 21.74 € + ~ 42.97 shipping

Wonders of globalization.

> >  the "killer" bargain: 10 Verbatims for ~ 46.11 € + free shipping!

Wow. That's only 20 times the price of regular DVD-R or DVD+R media.
(I see slightly cheaper offers for M-Disc BD-R 25 GB. Still 4 EUR per
piece while normal BD-R cost about 50 cents.)

Stefan Monnier wrote:
> I wonder if "archival quality" really serves its purpose here.  I mean,
> I understand that flash is not reliable in the long term, but there's
> also the problem of making sure you'll still have a working DVD reader
> in the future.

There are some reasons for hope:
The specifications of media and drive behavior are publicly available.
Lots of DVD and BD readers already exist. When rarely used they have a
long life span. (I recently bought a Lindy USB box for a SATA drive.
To my surprise it came with a SATA-IDE adapter. So i could use it for
my old CD burner of 2003.)
The separation of storage medium and storage device keeps the archive safer
against electronics failure.

Whether M-Disc is more reliable than organic dye discs has still to be
proven. 1000 years is a courageous goal. At least i'd demand glass discs
rather than polycarbonate.

> I thought the only reliable way to archive digital data would be to
> treat preservation as a *process*, where you "refresh" your archive
> every N years by copying it over to a newer media (with enough
> redundancy to detect and correct errors that may have crept in during
> those N years).

Indeed. It is important that archives get check-read regularly and that
there is more than one identical copy of each medium.
Optical media contain lots of error correction data. I add my own MD5s
on the filesystem level. (I have a BD-RE which one drive regards as fully
readable while all others and my MD5s say that a few blocks are damaged.)

The most important verification run is directly after burning. During the
last 20 years i never encountered a medium which later went bad without
showing visible signs of physical damage.

Have a nice day :)


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