Longevity of DVD-R and CD-R (Was MagTapes)

[Jim Leonard]

Eric Smith wrote:
> It was my understanding (perhaps wrong?) that RW media uses a phase
> change to store the data, and that it takes significantly more energy
> to induce the phase change than to induce a chemical change in dye
> for write-once media.  That's why it can't be written as quickly.
> If it really works that way, one would reasonably expect RW media to
> have *better* longevity than write-once media.

Based on my experience, this isn't true by a longshot.  After no less than 
three occaisions where I have lost data stored on DVD-RW media (all three with 
different media brands), I stopped doing it.  I only use rewritable media for 
testing burns now, never for archival storage.

As for the topic of "how long does DVD-R media last?", I feel it's irrelevant 
because newer, popular standards come along every decade and we retrofit our 
data to meet them as it inevitably grows.  From personal experience:

1985:  Stored my data on about 100 360K DSDD floppies
1990:  Purchased computer with 3.5" DSHD drive; copied my 360K floppies to 
about 25 DSHD disks.
1993:  Data grown to 200 DSHD floppies; stored all of them on single QIC tape.
1996:  Data grown to 4 QIC tapes; stored all four onto two CDRs.
2002:  Data grown to 200 CDRs (blame broadband!); spent a week merging 
duplicates and deleting redundant info, recompressing to more optimal formats, 
burnt them onto ~30 DVD-Rs.
2005:  Data grown to 200 DVD-Rs; archival storage is 3-4 DLT7000 tapes.

For extra paranoia, I never threw out any of the older medium (although I do 
recycle the disks as necessary, like when I need a spare 3.5" to make a boot 
disk or something).
-- 
Jim Leonard (trixter at oldskool.org)                    http://www.oldskool.org/
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