Reducing Uncertainty

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Reducing Uncertainty
National Institute of Standards and Technology
(NIST) Information Technology Laboratory Informat
ion Access Division Fred ByersNIST100 Bureau
Drive, Stop 8940 Gaithersburg, MD 20899 Email
byers_at_nist.gov
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Topics

• Consumer View
• Life Expectancy Test Issues
• Alternatives
• Benefits

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Manufacturers vs. Headlines
Consumer View

• Manufacturers
• Life Expectancy Best Case
• 100 300 years CD-Rs
• 60 100 years DVD-Rs
• Headlines
• Life Expectancy Worst Case
• CDs fail in short time frame
• 2 -10 years failure
• CD Rot

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Most Commonly Asked Question How long will my
(recordable) disc last? (CD-R, DVD-R, DVDR)
Consumer View

• Answer ? It depends on
• Care and handling
• Physical handling
• Environmental influences
• Initial recording quality
• Condition of disc before recording
• Quality of burn (depends on disc and burner)
• Disc construction
• Materials
• Manufacturing process

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More Consumer Questions
Consumer View

• Should I trust my digital content for long-term
  storage using these discs?
• Which disc should I buy?
• What is the minimum number of years I can expect?
• Does price make a difference?
• Does brand make a difference?
• What should I look for in a disc?
• Does the recorder make a difference?
• These above points are not unique to optical
  discs.

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What can the user control?
Consumer View

• ? Proper handling
• No scratches, etc.
• ? Proper storage
• Controlled at recommended storage conditions
• ? Initial recording quality
• Good disc clean, defect free, good recorder
• ? Disc construction
• Dependant on manufacturer

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- Relatively New -Long-Term Quality Discs
Consumer View

• Archive, or long-term labeled discs are available
  from some manufacturers
• What does it mean?
• How are they different from regular discs?
• How many years will they last? Longer LE?
• How does manufacturer A compare to manufacturer
  B?
• How are they determined to be longer lasting?

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Disc-Test Proposal
Consumer View

• A test to measure for minimum longevity
  expectation
• A test that can be performed in a reasonable time
  for manufacturers
• An indicator to consumers about minimum quality
• A minimum longevity that consumers can use for
  planning

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Why
Consumer View

• Variation in life expectancy among discs
• Quality differences between brands
• Quality differences within brands
• General claims of up to 100 years LE (DVD?R)
• Actual could be as low as 30 years in normal
  ambient room conditions
• Some anecdotal stories conflicting with general
  claims
• User confidence/uncertainty/awareness
• Consumer expectations - uncertain or unrealistic
• Planning under uncertainty refreshing, sampling
  and migration

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Consumer View
DVD-R Accelerated Aging Comparison Examples
PIE from Metal-Halide Light
PIE fromHigh T and RH
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Life Expectancy (LE) Test Standards
Consumer View

• Existing LE Test Method Standards
• CD-ROM
• ISO 189252002, AES 28-1997, ANSI/NAPM IT9.21
• CD-R
• ISO 189272002, AES 38-2000

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LE Testing Issues
LE Issues

• Time duration
• Typically one to two years
• Time to market
• Capability
• Equipment
• Space
• Expertise
• Cost
• Labor
• Contract out

• Existing LE Test Followed?
• No Standard DVD Test
• No Standard LE Test for DVD yet
• NIST is proposing a DVD procedure following the
  CD Standard
• No Standard archive quality test methodology
• NIST proposing a model

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LE - Accelerated Aging Times
LE Issues
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Incubation Testing Time
LE Issues
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Alternatives to the Existing LE Test (to save
time and cost)
Alternatives

• Shorten the LE Test
• Less expensive
• but
• Less accurate
• Initial Error Rate Test
• Measures initial quality of data on disc
• but
• Does not account for disc degradation rate
• Does not indicate life expectancy
• Target Test - Archival, or Longevity or
  Grade
• Longevity specific, i.e. minimum number of years
  expected
• Not a test to determine total disc LE

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Alternatives Continued
Alternatives

• Shorten the LE test
• Creates higher uncertainty for total disc LE
  measurement
• But
• Uncertainty level should still be acceptable for
  a lower limit
• Consider error increase-rate
• gt x fail
• Consider initial measurement?
• BLER-max gt x not acceptable
• Reflectance lt x not acceptable

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Another Approach
Alternatives

• Dont calculate for LE (T50) but make it a known
  lower limit.
• Example
• Make LE (or T50) 50 years lower limit.
• (At storage conditions 20ºC, 50RH)
• Determine from stress tests if disc will perform
  beyond the lower limit.

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Existing Equation from CD Standard
Alternatives

• Existing equation from CD-R Standard
• T50 Ae?H/kTe(B)RH or lnT50 lnA
  ?H/kT (B)RH
• T50 Time duration for median disc in a test-set
  to reach BLER-max (220).
• A, ?H and B determines the rate at which median
  disc reaches maximum allowed errors (220).
• Normally we derive A, ?H and B from test data,
  then calculate for T50.

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Alternative Use of Existing Equation
Alternatives

• Using T50 Ae?H/kTe(B)RH or lnT50 lnA
  ?H/kT (B)RH
• Instead of calculating for T50, make T50 known.
• For example T50 50 years
• (disc reaches BLER-max of 220 in 50 years at a
  given T and RH)
• Find A and combined e coefficients (?H and B) for
  T50 50yrs

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First Stress Test Set500 hour intervals x 4
80?C, 85RH
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Targeted Time Periods?(Sunscreen Approach)
Alternatives

• Can have more than one target or establish only
  one target.
• Total disc LE is unknown (not necessary)
• gt 30 yrs
• gt 50 yrs
• gt 75 yrs
• gt 100 yrs
• A test for one targeted minimum longevity time
  period
• 50 year example
• Discs are expected to extrapolate to beyond the
  lower-limit threshold.
• Error rate increases less than an established
  maximum acceptability

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What will this do for the Consumer? Consumer
Indecision Revisited
Consumer View

• Should I trust my digital content for long-term
  storage using these discs? (Properly tested
  discs, yes)
• Which disc should I buy? (Tested discs)
• What is the minimum number of years that I can
  expect? (As labeled)
• Will price make a difference? (Maybe)
• Will brand make a difference? (Maybe quality
  control consistency)
• What should I look for in a disc? (Label showing
  that the disc batch has passed the test)
• Does the recorder make a difference? (Maybe, same
  as before)

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Consumer/Industry Benefits
Benefits

• Consumer
• Consumer uncertainty reduced
• More informed choice for consumer
• Increase consumer confidence
• More realistic consumer expectation
• Consumer purchasing can be based on needs or
  migration plans
• Industry
• Industry-wide standard test
• Self-test or third party
• Time to market
• Testing cost (compared to existing LE testing)
• Pricing (cost recovery for implementing new
  procedure)

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What Is Needed From You, The User
Consumer View

• Define what archival means to you or what
  length of time needed for long-term storage.
• What is the minimum length of time needed for a
  disc to last to satisfy your requirements?
• What is the ideal length of time?
• Will this make a difference in your purchasing
  decision?
• Will you look for these labeled discs for
  long-term storage applications instead of other
  discs?

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Other ideas

• Early warning indicator
• RFID

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Early Warning Indicator

• Could also be called
• Error Alert
• Check Disc
• A warning about error rates that are approaching
  BLER max or PIE max.
• May also consider Burst errors
• Just a light as an indicator or a pop-up window
• Gives the actual number (good for initial error
  rate)

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• Thank you!
• NIST
• Information Access Division
• Information Technology Laboratory
• Digital Data Preservation
• Fred Byers, Oliver Slattery, Jian Zheng
• http//www.itl.nist.gov/div895/preservation/
• Care and Handling Guide
• http//www.itl.nist.gov/div895/carefordisc/

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Second Stress Test Set 500 hour intervals x 4
LE Issues
80?C, 70RH
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Third Stress Test Set 500 hour intervals x 4
LE Issues
80?C, 55RH
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Fourth Stress Test Set 750 hour intervals x 4
LE Issues
70?C, 85RH
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Fifth Stress Test Set 1000 hour intervals x 4
LE Issues
60?C, 85RH