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

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 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


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?”


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


Media Stability StudiesMedia Stability StudiesAging

Failure AnalysisModeling

Extrapolation


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


Media LifetimesMedia Lifetimes

1020

35

????

? How long willHow long willmy tapes last?my tapes last?

27 years


……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


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


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 ! !


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


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)


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


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


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


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


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


Accelerated Aging - TapeAccelerated Aging - Tape


CD-ROM: DurabilityCD-ROM: Durability

Source: Bill Murray, “CD-ROM Archivability,” NML Bits, 2(2), 4 (1992)


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


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


Optical Disk StructureOptical Disk Structure

protective coat

“data” layer

substrate

laser path

reflectivemetal (Al)

laser path

WORM / M-O CD-ROM / CD-R


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


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


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)


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

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

Documents

national media laboratory

estimates of media longevity

storage temperature

storage environment

rh slide

set of data

data files

government needs