1. NATIONAL MEDIA LABORATORY Storage Media Life Expectancies John Van Bogart National Media Laboratory Digital Archive Directions (DADs) Workshop June 22, 1998

2. NATIONAL MEDIA LABORATORY National Media Laboratory  Mission: To ensure that the U.S. Government leads the world in information superiority by working with commercial industry to catalyze, influence, and exploit emerging information technology and products that satisfy government needs.  NML Home Page address:  http://www.nml.org

3. NATIONAL MEDIA LABORATORY NML Media Stability Studies Since 1989 Since 1989 To provide solutions to U.S. Government data storage system issues. To provide solutions to U.S. Government data storage system issues. - Technology assessment - System reliability studies - Media stability studies To answer the question: “How long will my data files be accessible?” To answer the question: “How long will my data files be accessible?”

4. NATIONAL MEDIA LABORATORY Disposition/LE Chart For storage at 20°C (68°F) & 40% RH

5. NATIONAL MEDIA LABORATORY Media Stability Studies Aging Failure Analysis Modeling Extrapolation

6. NATIONAL MEDIA LABORATORY Accelerated Aging - Tape

7. NATIONAL MEDIA LABORATORY Media Lifetimes 10 20 35 ? ? ? ? ? How long will my tapes last? 27 years

8. NATIONAL MEDIA LABORATORY …your LE may vary... The quality with which the media was manufactured -- manufacturers and lots vary in quality The quality with which the media was manufactured -- manufacturers and lots vary in quality The storage temperature and humidity The storage temperature and humidity The cleanliness of the storage environment The cleanliness of the storage environment The care with which the media is handled The care with which the media is handled The number of times the media is accessed over its lifetime The number of times the media is accessed over its lifetime The quality of the recorder used to read/write to the media The quality of the recorder used to read/write to the media  Technological obsolescence

9. NATIONAL MEDIA LABORATORY CD-ROM: Durability Source : Bill Murray, “CD-ROM Archivability,” NML Bits, 2(2), 4 (1992)

10. NATIONAL MEDIA LABORATORY LE - Qualifying To completely qualify a LE value: To completely qualify a LE value: - Temperature - Humidity - Failure Criterion  Property & Value - Percent Surviving - Confidence Interval The same set of data can give many different LE values ! ! The same set of data can give many different LE values ! !

11. NATIONAL MEDIA LABORATORY AES/ANSI IT9-5 JTC Write standards for estimates of media longevity Write standards for estimates of media longevity Write standards for storage, handling, and transfer Write standards for storage, handling, and transfer Meets twice a year (June & Dec.) Meets twice a year (June & Dec.) Representatives from industry, government, and academia Representatives from industry, government, and academia IBM Imation Kodak Quantegy NARA NIST Library of Congress

12. NATIONAL MEDIA LABORATORY ANSI LE (Existing) Life Expectancy of Compact Discs (CD-ROM) (IT 9.21) Life Expectancy of Compact Discs (CD-ROM) (IT 9.21) Polyester Base Magnetic Tape - Storage (IT 9.23) Polyester Base Magnetic Tape - Storage (IT 9.23) Life Expectancy of Magneto-Optic (MO) Disks (IT 9.26) Life Expectancy of Magneto-Optic (MO) Disks (IT 9.26)

13. NATIONAL MEDIA LABORATORY ANSI: LE of CD-ROM  Failure:10 second average of the block error rate (BLER, ISO/IEC 10149) >= 220  Eyring acceleration model  Weibull failure distribution model  Report LE: “At a storage condition of 25° C and 50% RH, 95% of the product evaluated will last __ years, with 95% confidence.”

14. NATIONAL MEDIA LABORATORY LE: High Grade VHS Tape

15. NATIONAL MEDIA LABORATORY Storage Conditions Past Past - 70° F (21° C) & 50% RH (SMPTE - 1982) - 65° F (18° C) & 40% RH (NARA-1990) Future (ANSI, SMPTE,... ) Future (ANSI, SMPTE,... ) - For easy access:  60 - 74° F (15 - 23° C)  30 - 55% RH - Extended term storage:  As low as 50° F (10° C)  As low as 20% RH

16. NATIONAL MEDIA LABORATORY ANSI (In Draft) In Draft In Draft - LE of CD-R - LE of Magnetic Tape - Handling of Magnetic Tape - Storage of Optical Disc (IT 9.25) Proposed Proposed - LE of DVD - Light Stability of CD-R

17. NATIONAL MEDIA LABORATORYConclusions To preserve digital information To preserve digital information - Knowledge of media longevity is essential - Transcription is inevitable ANSI/AES JTC ANSI/AES JTC - Standard LE methods - Storage/Handling guidelines Future needs Future needs - Use of ANSI test methods -- publish LE ratings for media - Systems that monitor bit errors and warn of imminent media/drive failures

18. NATIONAL MEDIA LABORATORY Accelerated Aging - Tape

19. NATIONAL MEDIA LABORATORY CD-ROM: Durability Source : Bill Murray, “CD-ROM Archivability,” NML Bits, 2(2), 4 (1992)

20. NATIONAL MEDIA LABORATORY Tape - what can go wrong? Pigment -Loss of magnetic signal Deterioration of particle Self-demagnetization Binder - Polyester Polyurethane Hydrolysis - "Sticky" tape phenomenon - Debris/head clogs Lubricant Loss Substrate -Dimensional Changes - Mis-tracking Top Coat Back Coat Binder Substrate (PET) Pigment

21. NATIONAL MEDIA LABORATORY Binder Breakdown High Friction Low Cohesion Low Adhesion Low Coating Modulus Temporary Data Loss Permanent Data Loss Equipment/ Tape Damage Head Clogs Dropouts Tape Shedding Seizing Binder Hydrolysis

22. NATIONAL MEDIA LABORATORY Optical Disk Structure protective coat “data” layer substrate laser path reflective metal (Al) laser path WORM / M-OCD-ROM / CD-R

23. NATIONAL MEDIA LABORATORY For a 100 year life... Necessary to archive system along with the media Necessary to archive system along with the media Sufficient supply of spares for wearable parts (heads, LED’s, drive motors) Sufficient supply of spares for wearable parts (heads, LED’s, drive motors) Sufficient number of “new” systems to replace irreparable, worn out “old” systems Sufficient number of “new” systems to replace irreparable, worn out “old” systems Application software and host to “read” the data Application software and host to “read” the data Technical expertise / service manuals Technical expertise / service manuals

24. NATIONAL MEDIA LABORATORY Archival Storage Technology Look for industry accepted standards Look for industry accepted standards - Ensures compatibility of media - Interchangeability with other drives - Be wary of proprietary designs Is it a widely used technology? Is it a widely used technology? - Tends to “guarantee” the permanence of technology - Equipment, parts, support readily available - Less expensive Established Migration Path? Established Migration Path? Beware of emerging technologies Beware of emerging technologies - No track record, no standards, no market

25. NATIONAL MEDIA LABORATORY Change in Magnetic Remanence at 75C - 90% RH WEEKS -10 0 -20 -30 -40 -50 -60 -70 -80 1 35791113 150 24681012 1416 NML ßCam SP Model D2-a D2-b D2-c (4/91) D2-d D2-e D2-f D2-c (10/91)

26. NATIONAL MEDIA LABORATORY Digital Media vs. Film & Paper Digital media is not as stable Digital media is not as stable - Lower practical lifetimes (10 - 30 years) Catastrophic failures Catastrophic failures - Difficult to assess “health” of the storage medium Transcription required at regular intervals to preserve information Transcription required at regular intervals to preserve information Rapid advances in technology Rapid advances in technology Prevalence of several formats/ types Prevalence of several formats/ types