Are your CDs dying?

Discussion in 'Android Tablet Audio' started by Spider, May 16, 2014.

  1. Spider

    Spider Administrator Staff Member

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    Summary: Perhaps you thought that since music CDs are mechanically stamped and sealed in tough plastic, they'd last forever. Wrong! Some may already be dead. Here's why.

    [​IMG] By Robin Harris for Storage Bits |May 16, 2014 -- 12:34 GMT (05:34 PDT)

    Take two copies of the same manufactured CD from 1987 and subject to extreme heat and humidity in an environmental test chamber. Should turn out the same, right? No:

    [​IMG]
    Photo: Library of Congress

    The one of the right is totally destroyed, while the one on the left is still playable. Why?

    Commercially reproduced CDs — the kind from major music labels — are manufactured using a physical stamping on the plastic which is given a metallic coating to reflect the laser light - a physical imprint on the media. Writable CDs and most writable DVDs and Blu-rays use a chemical organic dye layer that is inherently unstable and will often die within five years.

    According to the Library of Congress, even commercial CDs made in the same year by the same company can have very different production processes leading to startling differences in failure rates and modes. For example:

    • Edge rot. Oxygen seeps through the plastic and reacts with the metal layer.
    • Bronzing. Corrosion due to pollutants in the air.
    • Laser burn. Player lasers also differ and some may shorten CD life.
    • Mis-handling. Bad scratches, yes, but also stickers and permanent marker writing on top.

    The Storage Bits take


    If you haven't already ripped your treasured CDs yet, now's the time! Whether you pick a lossless codec or high quality mp3, you can't rely on a commercial CD's quality to protect music you love.

    The LoC is researching this issue, in line with their mission to store and protect American history, through their Center for the Library's Analytical Scientific Samples (CLASS). They're putting together a database of scientific information on many kinds of media, including CDs.

    If there's something you want to save for the long term, consider writing it to an M-disc, whose non-organic write layer can sustain remarkable amounts of abuse (see Torture testing the 1,000-year DVD). It's the only media I'd trust for long-term digital storage — and only if I store copies in different places.
     
  2. Spider

    Spider Administrator Staff Member

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    Summary: Earlier this year company called Millenniata came out with a DVD that claimed a 1000 year life. Could that really be true?

    [​IMG] By Robin Harris for Storage Bits | November 14, 2013 -- 14:12 GMT (06:12 PST)

    When I say torture-tested, I'm not kidding. Here's a picture of a DVD that didn't survive:

    [​IMG]
    Another one bytes the dust!

    The M-disc uses a mineral medium between two standard plastic DVD layers. When written, a portion of the mineral material melts and forms a permanent readable pit. Other writable DVDs use an organic fluid dye layer which degrades over time.

    Using an M-disc logoed Blu-ray burner - today all LG drives support writing M-disc media - the disc is writable just like any other writable DVD. Next year drives from Samsung, Lite-on and others are expected to also support M-discs.

    But I've heard promises like this before and wanted to test it myself. Millenniata sent me an LG USB Blu-ray burner and some M-discs to try out.

    Test philosophy

    Standards-based accelerated life testing is like any other testing regimen. Products can be engineered to meet the test.

    For example, the use of the elevated temperatures in disk drive accelerated life testing gave us hard drives that are much less sensitive to temperature than people assumed. But it didn't mean the drives were necessarily long-lived - they just tested better.

    In my testing I took a much more brutal approach. I did things well outside any normal testing regimen. Why? Because any consumer is likely to do things that standards don't foresee - like sticking DVDs in a hot attic for 20 years.

    Test bed

    I collected about 4 GB of data: JPEGs; .mov and .mkv movies; PDFs and MP3s. I chose these because it would be easy to verify whether they were complete and accurate.

    Then I took all the written DVD-Rs and put them outside. Half of each DVD was protected from direct sun and the other half exposed to the weather which included snow, rain and weeks of blistering Arizona sunshine.

    Arizona - where I live - is not only a state, it is an environmental test chamber. Many Arizona place names relate to death: Dead Horse Ranch; Skull Valley; and Tombstone, famous for the gunfight at the OK Corral, to name a few. I live in the mountains of northern Arizona where it is usually 15F cooler than Phoenix, but this is still a tough desert environment.

    After several weeks of this totally beyond-any-known-spec treatment I brought the DVDs inside and ran them through a dishwasher - without the hot drying cycle - to get the crud off. Then I tried to read them.

    Results

    The cheap no-name store brand pictured above totally gave up the ghost. Large chunks of the reflective coating disappeared and, of course, the disc was unreadable.

    A Memorex DVD-R survived with coatings intact. When placed in my Apple SuperDrive it displayed the file info. But none were readable.

    But the M-discs not only survived, but all the files were readable on the SuperDrive, the original Blu-ray burner they were written on AND the .mkv movie file was readable on a Blu-ray player.

    Amazing! Here's what one M-disc looked like:

    [​IMG]
    One of several M-discs after weeks outside

    The Storage Bits take

    The M-disc team has done digital civilization a real service by building a reliable digital archive medium that is cheap - M-discs are available online for just over $2 each in bulk - tough, and widely usable with current technology. Color me impressed!

    Regular readers know that I often despair over the transitory nature of today's storage infrastructure. The fundamental problem is that the universe hates your data and, until now, we've had few strategies for overcoming that.

    I've been scanning hundreds of family photos and am putting together archive discs of those and other documents for my family. Until the M-disc I wouldn't have bothered because there was no trustworthy media to put them on. Now I believe there is.

    Is the M-disc technology perfect? No. Only about a dozen LG burners are certified to write M-discs, although other burners may be able to. Another catch: M-discs may not be readable by every DVD player. I didn't find it to be a problem with my Apple Superdrive or LG Blu-ray player, but Millenniata engineers noted that it could happen. But given the ubiquity of DVD and Blu-ray readers I don't think that is much of a problem: if one doesn't work, try another.

    But these are nits. If you have data you care about keeping for decades, the M-disc is the only game in town.

    Comments welcome. I have no business relationship with Millenniata now or planned and no money has changed hands, much to my accountant's distress. How would you use a reliable archive medium?

    Update: I added info on future drive vendor support from Millenniata and corrected some dictation-induced errors.
     

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