Steven's message below is a good summary of things as they stand, but my
feeling FWIW is that variations on multiple HD/RAID/LTO etc are likely
to become more affordable, easier to implement and more viable for an
increasing number of us, from national to personal archive keepers, to
the point where we may not need to worry about *long term* longevity of
those little shiny discs, if we're careful. 

At the British Library Sound Archive we take CD-R and DVD-R longevity
seriously, using more than one testing device within a testing strategy,
and it's all very labour intensive. The Library as a whole is working on
a mass storage setup, and as soon as we have access to that, we'll
ingest like crazy and ditch (or at least stop relying on) recordable
optical media ASAP. 

Steven said "So, if I read the tea interleaves correctly, it's one MAM
gold, two MAM golds if a backup is required." 

I reckon a good quality, appropriately burned silver backup is safer in
the *medium term* than a gold backup on batch-identical media. If we're
still relying solely on -R discs in 10 years time, I'll be deeply
depressed. (Which isn't to say it won't happen, of course...)

In the meantime, keep testing.


-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:[log in to unmask]] On Behalf Of Steven Smolian
Sent: 26 April 2006 15:13
To: [log in to unmask]
Subject: Re: [ARSCLIST] TY vs Mitsui. SUmmary

My previously unmade point exactly.  I couldn't come up with less than a

too-unwordy explanation, but, Joe, your succinctness works perfectly.

The issue of gold DVDs arose.  I understood that the chemistry was
from CDs and wonder if the former are effective for long term storage. 
There being no actual standard for audio DVDs is unsettling as well. Any

tests?   Looking 25 years into the future, will there be a problem
them to play back?

Someone wrote to the effect that test results from a manufacturer are
advertising.  I admit they are advertising, but perhaps not only.  It
a starting place to confirm, adjust or disprove the science rather than 
leaving a blank, "I wish we had data" void.

Kodak published their tests rather than the results only.  So, if I
did Mitsui.  TY, on the otherhand, made claims without such publically 
avaliable back-up.  I spoke to them at the time the ealy ads apperared,
was told that, since there were no testing standards, they chose those
made their product look best.

NIST's report on CDs gives much more conservative numbers for CD
even for gold ones, but the gold was vastly superior to everything else.

Since they never mention actual manufacturers, it took much deep thought
come up the the winner's brand name in a field of one.

Short of having a reliable server system continually refreshing the data
holds as it circulates among drives, gold CDs are the 44.1 answer.  Long

term storage of files with higher rates on finite objects is still 
unsettled, but  the feelgood solution seems to be gold DVDs.  Until
testing of the latter, they are feelgood only and should by no means be 
considered a standard.

Does that express the group's current state of mind on this thread?

Steve Smolian
----- Original Message ----- 
From: <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, April 26, 2006 8:47 AM
Subject: Re: [ARSCLIST] TY vs Mitsui

> How much of an error rate difference are we talking about?
> For sure, when you burn a disc, you want a low error rate and no E22
> E32 errors. However, all other things being equal if we are talking
> BLER of 0.5 versus BLER 3.0, this is not an issue.
> I have burned a large variety of discs on different burners and
> speeds for the research I have performed. The TY/cyanine does tend to
> produce a BLER <1 on many occasions. The Mitsui/MAM can attain this,
> the BLER is usually slightly higher (in the 2 to 3 range).
> That being said, gold metal layer will not corrode, silver alloy will.
> Phthalocyanine dye is very stable to light, heat, RH and cyanine is
> These points are not theoretical.
> So, as Jerry briefly pointed out as well, here is a basic example:
> Disc A (gold metal/phthalocyanine): Initial Bler = 10.0
> Disc B (silver metal/cyanine): Initial Bler =0.2
> Disc A is very stable and over 10 years does not change. However, Disc
> is
> less stable and does change over the 10 years due to exposure to one
> all
> of the following: light, elevated temperature and relative humidity,
> levels of pollutants from the atmosphere, or exposure from aggressive 
> agent
> from poor storage enclosures.
> After ten years you have:
> Disc A (gold metal/phthalocyanine): Ten year Bler = 10.8
> Disc B (silver metal/cyanine): Ten year Bler =100.0
> Where would you rather be?
> Joe
> -- 
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