Monday, August 03, 2015

How Long Is Long-Term Data Storage?

How Long Is Long-Term Data Storage? Barry Lunt. IS &T Archiving Conference. 2011.
    This paper looks at "In the context of archiving of physical documents, long-term storage has long been accepted to mean centuries." Since digital documents are much more ephemeral, archivists need to be aware of the technologies for preserving digital data and what can be expected for the long term. Results of several studies show that, with one notable exception, digital data cannot be expected to endure using any existing technologies.

Besides mechanical wear, oxidation, corrosion, and breaking of chemical bonds the most common failure mechanisms for materials, including digital data. Elevated temperature, humidity, and exposure to light increase the likelihood of failure, which is why archival storage relies on a controlled environment to reduce temperature, humidity and light.  The digital storage technologies, magnetic, solid-state, and optical, has known failure mechanisms, which have been studied. The studies of life expectancy for hard disk drives “eliminates HDDs as an archival storage option”.

The best way to guarantee that data will be readable in the future is by how widespread the adoption is. With data storage, "by far the most widespread formats in the history of digital data are the three main optical disc formats: CDs, DVDs and BDs". There are billions of optical readers in use today, and hundreds of billions of discs; no other digital storage technology even comes close.   While this does not guarantee long term persistence far into the future, the probability is extremely high. "If there is data still extant in these formats 500 years from now, it would be a relatively trivial matter to access that data".

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