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NATIONAL MEDIA LABORATORY
Storage MediaStorage MediaLife ExpectanciesLife Expectancies
John Van BogartJohn Van BogartNational Media LaboratoryNational Media Laboratory
Digital Archive Directions Digital Archive Directions (DADs) Workshop(DADs) Workshop
June 22, 1998June 22, 1998
NATIONAL MEDIA LABORATORY
National Media LaboratoryNational Media Laboratory Mission:Mission: To ensure that the U.S. To ensure that the U.S.
Government leads the world in Government leads the world in information superiority by working information superiority by working with commercial industry to catalyze, with commercial industry to catalyze, influence, and exploit emerging influence, and exploit emerging information technology and products information technology and products that satisfy government needs.that satisfy government needs.
NML Home Page address:NML Home Page address: http://www.nml.orghttp://www.nml.org
NATIONAL MEDIA LABORATORY
NML Media Stability StudiesNML Media Stability Studies
Since 1989Since 1989To provide solutions to U.S. To provide solutions to U.S.
Government data storage system issues.Government data storage system issues.- Technology assessmentTechnology assessment- System reliability studiesSystem reliability studies- Media stability studiesMedia stability studies
To answer the question: “How long will To answer the question: “How long will my data files be accessible?”my data files be accessible?”
NATIONAL MEDIA LABORATORY
Disposition/LE ChartDisposition/LE Chart
Magnetic Tape Optical Disk Paper Microfilm
Retention Period -
Required Storage Life I-
D1
Dat
a D
-2
Dat
a D
-3
3480
3490
/349
0e
DL
T
Dat
a 8m
m /
Dat
a V
HS
DD
S /
4m
m
QIC
/ Q
IC-w
ide
CD
-RO
M
WO
RM
CD
-R
M-O
New
spap
er (
hig
h l
ign
in)
Hig
h Q
ual
ity
(lo
w l
ign
in)
"Per
man
ent"
(b
uff
ered
)
Med
ium
-Ter
m F
ilm
Arc
hiv
al Q
ual
ity
(Sil
ver)
Retention Period -
Required Storage Life
1 year 1 year2 years 2 years5 years 5 years
10 years 10 years15 years 15 years20 years 20 years30 years 30 years50 years 50 years
For storage at 20°C (68°F) & 40% RH
NATIONAL MEDIA LABORATORY
Media Stability StudiesMedia Stability StudiesAging
Failure AnalysisModeling
Extrapolation
NATIONAL MEDIA LABORATORY
Accelerated Aging - TapeAccelerated Aging - TapeD1 Medium - EOT BER vs Time
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
0 100 200 300 400
Hours at Temperature
Bit
Err
or
Ra
te
Manufacturer's Limit
45°C50°C
55°C
60°C
NATIONAL MEDIA LABORATORY
Media LifetimesMedia Lifetimes
1020
35
????
? How long willHow long willmy tapes last?my tapes last?
27 years
NATIONAL MEDIA LABORATORY
……your LE may vary...your LE may vary... The quality with which the media was manufactured The quality with which the media was manufactured
-- manufacturers and lots vary in quality-- manufacturers and lots vary in quality The storage temperature and humidityThe storage temperature and humidity The cleanliness of the storage environmentThe cleanliness of the storage environment The care with which the media is handledThe care with which the media is handled The number of times the media is accessed over its The number of times the media is accessed over its
lifetimelifetime The quality of the recorder used to read/write to the The quality of the recorder used to read/write to the
mediamedia Technological obsolescenceTechnological obsolescence
NATIONAL MEDIA LABORATORY
CD-ROM: DurabilityCD-ROM: Durability
Source: Bill Murray, “CD-ROM Archivability,” NML Bits, 2(2), 4 (1992)
-100
0
100
200
300
400
500
600
700
0 1000 2000 3000
Hours at 60°C (140°F) / 85% Relative Humidity
% B
LER
(B
lock
Err
or R
ate)
In
crea
se
NATIONAL MEDIA LABORATORY
LE - QualifyingLE - Qualifying To completely qualify a LE value:To completely qualify a LE value:- TemperatureTemperature- HumidityHumidity- Failure CriterionFailure Criterion
Property & ValueProperty & Value
- Percent SurvivingPercent Surviving- Confidence IntervalConfidence Interval
The same set of data can give many The same set of data can give many different LE values ! !different LE values ! !
NATIONAL MEDIA LABORATORY
AES/ANSI IT9-5 JTCAES/ANSI IT9-5 JTCWrite standards for estimates of media Write standards for estimates of media
longevitylongevityWrite standards for storage, handling, and Write standards for storage, handling, and
transfertransferMeets twice a year (June & Dec.)Meets twice a year (June & Dec.)Representatives from industry, Representatives from industry,
government, and academiagovernment, and academiaIBM Imation Kodak Quantegy IBM Imation Kodak Quantegy
NARA NIST Library of CongressNARA NIST Library of Congress
NATIONAL MEDIA LABORATORY
ANSI LE (Existing)ANSI LE (Existing)
Life Expectancy of Compact Discs Life Expectancy of Compact Discs (CD-ROM) (IT 9.21)(CD-ROM) (IT 9.21)
Polyester Base Magnetic Tape - Polyester Base Magnetic Tape - Storage (IT 9.23)Storage (IT 9.23)
Life Expectancy of Magneto-Optic Life Expectancy of Magneto-Optic (MO) Disks (IT 9.26)(MO) Disks (IT 9.26)
NATIONAL MEDIA LABORATORY
ANSI: LE of CD-ROMANSI: LE of CD-ROM Failure:Failure: 10 second average of the block error rate (BLER, ISO/IEC 10 second average of the block error rate (BLER, ISO/IEC
10149) >= 22010149) >= 220 Eyring acceleration modelEyring acceleration model Weibull failure distribution modelWeibull failure distribution model Report LE: “At a storage condition of 25° C and 50% RH, 95% of the Report LE: “At a storage condition of 25° C and 50% RH, 95% of the
product evaluated will last __ years, with 95% confidence.”product evaluated will last __ years, with 95% confidence.”
Temp % RH # Spec. Incubation Min. Total Aging80° C 85 10 500 hr 2000 hr80° C 70 10 500 hr 2000 hr80° C 55 15 500 hr 2000 hr70° C 85 15 750 hr 3000 hr60° C 85 30 1000 hr 4000 hr
NATIONAL MEDIA LABORATORY
LE: High Grade VHS TapeLE: High Grade VHS Tape
20
25
30
35
40
45
50
15 20 25Temperature (C)
Re
lati
ve
Hu
mid
ity
(%
)
40 yrs
72 F & 50%
68 F & 40%
65 F & 30% RH
30 yrs20 yrs
15 yrs
10 yrs
NATIONAL MEDIA LABORATORY
Storage ConditionsStorage ConditionsPastPast- 70° F (21° C) & 50% RH (SMPTE - 70° F (21° C) & 50% RH (SMPTE -
1982)1982)- 65° F (18° C) & 40% RH (NARA-65° F (18° C) & 40% RH (NARA-
1990)1990)Future (ANSI, SMPTE, . . . )Future (ANSI, SMPTE, . . . )- For easy access:For easy access:
60 - 74° F (15 - 23° C)60 - 74° F (15 - 23° C) 30 - 55% RH30 - 55% RH
- Extended term storage:Extended term storage: As low as 50° F (10° C)As low as 50° F (10° C) As low as 20% RHAs low as 20% RH
NATIONAL MEDIA LABORATORY
ANSI (In Draft)ANSI (In Draft) In DraftIn Draft- LE of CD-RLE of CD-R
- LE of Magnetic TapeLE of Magnetic Tape
- Handling of Magnetic TapeHandling of Magnetic Tape
- Storage of Optical Disc (IT 9.25)Storage of Optical Disc (IT 9.25)
ProposedProposed- LE of DVDLE of DVD
- Light Stability of CD-RLight Stability of CD-R
NATIONAL MEDIA LABORATORY
ConclusionsConclusionsTo preserve digital informationTo preserve digital information- Knowledge of media longevity is essentialKnowledge of media longevity is essential- Transcription is inevitableTranscription is inevitable
ANSI/AES JTCANSI/AES JTC- Standard LE methods Standard LE methods - Storage/Handling guidelinesStorage/Handling guidelines
Future needsFuture needs- Use of ANSI test methods -- publish LE Use of ANSI test methods -- publish LE
ratings for mediaratings for media- Systems that monitor bit errors and warn of Systems that monitor bit errors and warn of
imminent media/drive failuresimminent media/drive failures
NATIONAL MEDIA LABORATORY
CD-ROM: DurabilityCD-ROM: Durability
Source: Bill Murray, “CD-ROM Archivability,” NML Bits, 2(2), 4 (1992)
NATIONAL MEDIA LABORATORY
Tape - what can go wrong?Tape - what can go wrong?
Pigment -Loss of magnetic signal Deterioration of particle Self-demagnetizationBinder - Polyester Polyurethane Hydrolysis
- "Sticky" tape phenomenon - Debris/head clogs Lubricant Loss
Substrate -Dimensional Changes - Mis-tracking
Top Coat
Back Coat
Binder
Substrate (PET)
Pigment
NATIONAL MEDIA LABORATORY
Binder Breakdown Binder Breakdown
High Friction
Low Cohesion
Low Adhesion
Low CoatingModulus
TemporaryData Loss
Permanent Data Loss
Equipment/Tape Damage
Head ClogsDropouts
Tape SheddingSeizing
Binder Hydrolysis
NATIONAL MEDIA LABORATORY
Optical Disk StructureOptical Disk Structure
protective coat
“data” layer
substrate
laser path
reflectivemetal (Al)
laser path
WORM / M-O CD-ROM / CD-R
NATIONAL MEDIA LABORATORY
For a 100 year life . . .For a 100 year life . . .Necessary to archive system along with Necessary to archive system along with
the mediathe mediaSufficient supply of spares for wearable Sufficient supply of spares for wearable
parts (heads, LED’s, drive motors)parts (heads, LED’s, drive motors)Sufficient number of “new” systems to Sufficient number of “new” systems to
replace irreparable, worn out “old” replace irreparable, worn out “old” systemssystems
Application software and host to “read” Application software and host to “read” the datathe data
Technical expertise / service manualsTechnical expertise / service manuals
NATIONAL MEDIA LABORATORY
Archival Storage TechnologyArchival Storage TechnologyLook for industry accepted standardsLook for industry accepted standards- Ensures compatibility of mediaEnsures compatibility of media- Interchangeability with other drivesInterchangeability with other drives- Be wary of proprietary designsBe wary of proprietary designs
Is it a widely used technology?Is it a widely used technology?- Tends to “guarantee” the permanence of technologyTends to “guarantee” the permanence of technology- Equipment, parts, support readily availableEquipment, parts, support readily available- Less expensiveLess expensive
Established Migration Path?Established Migration Path?Beware of emerging technologiesBeware of emerging technologies- No track record, no standards, no marketNo track record, no standards, no market
NATIONAL MEDIA LABORATORY
Change in Magnetic Remanence Change in Magnetic Remanence at 75C - 90% RHat 75C - 90% RH
WEEKS
-10
0
-20
-30
-40
-50
-60
-70
-80
1 3 5 7 9 11 13 150 2 4 6 8 10 12 14 16
NML ßCam SP Model
D2-aD2-bD2-c (4/91)
D2-d
D2-e
D2-f
D2-c (10/91)
NATIONAL MEDIA LABORATORY
Digital Media vs. Film & PaperDigital Media vs. Film & Paper
Digital media is not as stableDigital media is not as stable- Lower practical lifetimes (10 - 30 years)Lower practical lifetimes (10 - 30 years)
Catastrophic failuresCatastrophic failures- Difficult to assess “health” of the storage Difficult to assess “health” of the storage
mediummediumTranscription required at regular Transcription required at regular
intervals to preserve informationintervals to preserve informationRapid advances in technologyRapid advances in technologyPrevalence of several formats/ typesPrevalence of several formats/ types
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