1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationImaging materials Information stored on magneto-optical (MO) discs Method for estimating the life expectancy based on the effects of temperature and relative humidityBS ISO 18926
2、:2012National forewordThis British Standard is the UK implementation of ISO 18926:2012. It supersedes BS ISO 18926:2006 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee CPW/42, Photography.A list of organizations represented on this committee can be obt
3、ained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2012Published by BSI Standards Limited 2012ISBN 978 0 580 76595 7 ICS 35.220.30; 37.040.99Co
4、mpliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 June 2012.Amendments issued since publicationDate Text affectedBRITISH STANDARDBS ISO 18926:2012 ISO 2012Imaging
5、 materials Information stored on magneto-optical (MO) discs Method for estimating the life expectancy based on the effects of temperature and relative humidityMatriaux pour limage Information stocke sur disques opto-magntiques (MO) Mthode destimation de lesprance de vie base sur les effets de la tem
6、prature et de lhumidit relativeINTERNATIONAL STANDARDISO18926Second edition2012-06-01Reference numberISO 18926:2012(E)BS ISO 18926:2012ISO 18926:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may
7、 be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 4
8、1 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 18926:2012ISO 18926:2012(E) ISO 2012 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope 12 Purpose and assumptions 12.1 Purpose 12.2 Assumptions . 13 Normative references . 14 Te
9、rms and definitions . 25 Measurements 35.1 Summary 35.2 Byte error rate (BER) 35.3 Test equipment . 45.4 Test specimen 46 Accelerated stress test plan . 46.1 General . 46.2 Stress conditions 56.3 Accelerated test cell sample population . 76.4 Time intervals . 77 Data evaluation 77.1 Lognormal distri
10、bution model . 77.2 Eyring acceleration model 87.3 Acceleration factor 97.4 Survivor analysis . 98 Disclaimer 10Annex A (normative) Ten-step analysis outline 11Annex B (informative) Example of a test plan and data analysis 12Bibliography .21BS ISO 18926:2012ISO 18926:2012(E)ForewordISO (the Internat
11、ional Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has bee
12、n established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical stand
13、ardization.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for v
14、oting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all su
15、ch patent rights.ISO 18926 was prepared by Technical Committee ISO/TC 42, Photography.This second edition cancels and replaces the first edition (ISO 18926:2006), of which it constitutes a minor revision with the following changes: the original Annex A has been removed and the remaining annexes have
16、 been reidentified; in Clause 3, references to ISO/IEC 17346:2005, ISO/IEC 22092:2002 and ISO/IEC 22533:2005 have been added; in 6.2.4, Table 2, the bottom line temperature has been changed from 25 C to 23 C; in 7.3, Formula (4), the temperature has been changed from 25 C to 23 C; in Annex B, the te
17、mperature in the first sentence of the paragraph above Table B.6 has been changed from 298,1 K to 296,1 K; in Annex B, the temperature in the second paragraph below Figure B.5 has been changed from 25 C to 23 C.iv ISO 2012 All rights reservedBS ISO 18926:2012ISO 18926:2012(E)IntroductionThis Interna
18、tional Standard is one of a series of standards dealing with the physical properties and stability of imaging materials. ISO 2012 All rights reserved vBS ISO 18926:2012Imaging materials Information stored on magneto-optical (MO) discs Method for estimating the life expectancy based on the effects of
19、 temperature and relative humidity1 ScopeThis International Standard specifies a test method for estimating the life expectancy (LE) of information stored on rewritable and write-once magneto-optical media. Only the effects of temperature and relative humidity on the media are considered.2 Purpose a
20、nd assumptions2.1 PurposeThe purpose of this International Standard is to establish a methodology for estimating the life expectancy of information stored on magneto-optical discs. This methodology provides a technically and statistically sound procedure for obtaining and evaluating accelerated test
21、 data.2.2 AssumptionsThe validity of the procedure defined by this International Standard relies on five assumptions: the failure mechanisms acting at the usage conditions are the same as those at the accelerated conditions; the linearity of the byte error rate (BER) estimated over the accelerated a
22、nd design conditions is valid; all failure mechanisms have been accounted for and appropriately modelled; failure caused by reversible effects such as surface dust is not included; failure from repairable parts such as external cartridge components is not included.3 Normative referencesThe following
23、 referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO/IEC 10089:1991, Information technology 130 mm rewritable op
24、tical disk cartridge for information interchangeISO/IEC 10090:1992, Information technology 90 mm optical disk cartridges, rewritable and read only, for data interchangeISO/IEC 11560:1992, Information technology Information interchange on 130 mm optical disk cartridges using the magneto-optical effec
25、t, for write once, read multiple functionalityISO/IEC 13549:1993, Information technology Data interchange on 130 mm optical disk cartridges Capacity: 1,3 gigabytes per cartridgeISO/IEC 13963:1995, Information technology Data interchange on 90 mm optical disk cartridges Capacity: 230 megabytes per ca
26、rtridgeISO/IEC 14517:1996, Information technology 130 mm optical disk cartridges for information interchange Capacity: 2,6 Gbytes per cartridgeINTERNATIONAL STANDARD ISO 18926:2012(E) ISO 2012 All rights reserved 1BS ISO 18926:2012ISO 18926:2012(E)ISO/IEC 15041:1997, Information technology Data inte
27、rchange on 90 mm optical disk cartridges Capacity: 640 Mbytes per cartridgeISO/IEC 15286:1999, Information technology 130 mm optical disk cartridges for information interchange Capacity: 5,2 Gbytes per cartridgeISO/IEC 17346:2005, Information technology Data interchange on 90 mm optical disk cartrid
28、ges Capacity: 1,3 Gbytes per cartridgeISO/IEC 22092:2002, Information technology Data interchange on 130 mm magneto-optical disk cartridges Capacity: 9,1 Gbytes per cartridgeISO/IEC 22533:2005, Information technology Data interchange on 90 mm optical disk cartridges Capacity: 2,3 Gbytes per cartridg
29、eAitchison, J. and Brown, J.A.C., The Lognormal Distribution, Cambridge University Press, 19574 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.4.1baselinecondition representing the disc at time of manufactureNOTE This is customarily the initial para
30、meter measurement taken prior to any application of stress. The designation is usually t = 0 for a stress time equal to zero hours.4.2byte error rateBERnumber of bytes in error divided by number of bytes testedNOTE BER refers to the raw byte error rate, without benefit of any error correction or sec
31、tor re-allocation.4.3censored datatime at which a specimen is removed from life testing due to any reason other than having reached end-of-life4.4end-of-lifeoccurrence of any loss of information4.5informationsignal or image recorded using the system4.6F(t)probability that a random unit drawn from th
32、e population fails by the time t, or the fraction of all units in the population which fail by time t4.7life expectancyLElength of time that information is predicted to be retrievable in a system under extended-term storage conditions4.7.1standardized life expectancySLEminimum life span, predicted w
33、ith 95 % confidence, of 95 % of the product stored at a temperature not exceeding 23 C and a relative humidity (RH) not exceeding 50 %2 ISO 2012 All rights reservedBS ISO 18926:2012ISO 18926:2012(E)4.8magneto-optical discany disc conforming to the ISO/IEC standards contained in Clause 3NOTE Double-s
34、ided media are considered to be composed of two discs, one per side. In general, a magneto-optical disc is one that uses thermo-magnetic properties for recording and opto-magnetic properties for reading.4.9R(t)probability that a unit drawn from the population will survive at least time t, or the fra
35、ction of units in the population that will survive at least time tNOTE R(t) = 1 F(t)4.10retrievabilityability to access information as recorded4.11stressexperimental variable to which the specimen is exposed for the duration of the test intervalNOTE In this International Standard, the stress variabl
36、es are confined to temperature and relative humidity.4.12systemcombination of recording medium, hardware, software and documentation necessary to retrieve information4.13test celldevice that controls the stress to which the specimen is exposed4.14test patterndistribution of 1s and 0s within a sector
37、5 Measurements5.1 SummaryA sampling of 80 discs is baseline tested for the BER, then divided into five groups according to a specified plan. Each group of discs is subjected to one of five combinations of temperature and relative humidity (stress). During the exposure to the stress condition, discs
38、are periodically removed from the environmental test cell according to a set plan. These discs are then retested for BER and subsequently returned to the test cell for additional increments of exposure at the same stress.For each disc, the time to reach end-of-life (loss of any information or BER 5
39、104), is then determined or estimated. For each stress condition, the resulting service life data are fitted to a lognormal distribution for that stress. These five sets of parameters (lifetime, temperature and relative humidity) are regressed to fit an Eyring acceleration model. This model is then
40、used to estimate the distribution of lifetimes at a standardized set of conditions.5.2 Byte error rate (BER)The objective of measuring the BER is to establish a practical estimation of the systems ability to read previously written bits using a standard drive. This International Standard considers B
41、ER to be a reasonable estimate of the performance of the system. A change in the BER in response to the time at the accelerated temperature and humidity is the principal degradation parameter. ISO 2012 All rights reserved 3BS ISO 18926:2012ISO 18926:2012(E)The true end-of-life for any data storage m
42、edia is any loss of information. Ideally, each specimen is tested until actual failures occur. The first occurrence of any disc degradation that results in uncorrectable errors is considered to signal the actual end-of-life.Realistically, testing until all discs have failed is impractical. For the p
43、urposes of this International Standard, the maximum average BER shall be 5,0 104if actual failures do not occur during testing. This is very system dependent and its use here is an arbitrary level chosen as a conservative prediction of the onset of unacceptable errors and thereby the end of disc lif
44、e. All BER measurements are made with the system error correction switched off.5.3 Test equipment5.3.1 GeneralAny disc drive system that conforms to ISO/IEC standards (see Clause 3) may be used. The tester shall be capable of reporting errors occurring prior to the implementation of error correction
45、 systems.5.3.2 Calibration and repeatabilityA control disc shall be maintained and measured before and after each data collection interval. For each test drive, a control chart shall be maintained for this control disc with plus or minus three sigma action limits. The mean and standard deviation of
46、the control disc shall be established by collecting at least five measurements. If any individual BER reading lies outside the action limits, the problem shall be corrected and all data collected since the last valid control point shall be remeasured.If it becomes necessary to replace the test drive
47、, the new drive shall be calibrated using the control disc and compared to the replaced drive. If a statistical difference exists between the control disc BER means, subtract the new disc mean from the old disc mean and add this correction factor to all subsequent BER measurements made with the new
48、drive.5.4 Test specimenA test specimen is any disc that conforms to ISO/IEC specifications referenced in Clause 3 and contains representative data written over 100 % of the user area. Representative data may be real data or random test data.6 Accelerated stress test plan6.1 GeneralA well manufacture
49、d magneto-optical disc should last several years or even decades. As such, it is not practical to conduct life studies under normal usage conditions. It is then necessary to conduct accelerated aging studies in order to determine the estimated potential for life of this medium. To be successful, these studies shall be planned ahead of time in order to be of sound design both technically and statistically.Many accelerated life test plans follow a rather tradit
