Approaches to Preservation Storage Technologies
 

Approaches to Preservation Storage Technologies

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The structure and design of digital storage systems is a cornerstone of digital preservation. To better understand ongoing storage practices of organizations committed to digital preservation, the ...

The structure and design of digital storage systems is a cornerstone of digital preservation. To better understand ongoing storage practices of organizations committed to digital preservation, the National Digital Stewardship Alliance conducted a survey of member organizations. This talk discusses findings from this survey, common gaps, and trends in this area.

(I also have a little fun highlighting the hidden assumptions underlying Amazon Glacier's reliability claims. For more on that see this earlier post: http://drmaltman.wordpress.com/2012/11/15/amazons-creeping-glacier-and-digital-preservation )

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  • This work. by Micah Altman (http://micahaltman.com) is licensed under the Creative Commons Attribution-Share Alike 3.0 United States License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/3.0/us/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.
  • The structure and design of digital storage systems is a cornerstone of digital preservation. To better understand ongoing storage practices of organizations committed to digital preservation, the National Digital Stewardship Alliance conducted a survey of member organizations. This talk discusses findings from this survey, common gaps, and trends in this area.(I also have a little fun highlighting the hidden assumptions underlying Amazon Glacier's reliability claims. For more on that see this earlier post: http://drmaltman.wordpress.com/2012/11/15/amazons-creeping-glacier-and-digital-preservation )

Approaches to Preservation Storage Technologies Approaches to Preservation Storage Technologies Presentation Transcript

  • Prepared for MIT Libraries Informatics Program Brown Bag Talk June 2013 Approaches to Preservation Storage Technologies Dr. Micah Altman <escience@mit.edu> Director of Research, MIT Libraries
  • DISCLAIMER These opinions are my own, they are not the opinions of MIT, Brookings, any of the project funders, nor (with the exception of co-authored previously published work) my collaborators Secondary disclaimer: “It’s tough to make predictions, especially about the future!” -- Attributed to Woody Allen, Yogi Berra, Niels Bohr, Vint Cerf, Winston Churchill, Confucius, Disreali [sic], Freeman Dyson, Cecil B. Demille, Albert Einstein, Enrico Fermi, Edgar R. Fiedler, Bob Fourer, Sam Goldwyn, Allan Lamport, Groucho Marx, Dan Quayle, George Bernard Shaw, Casey Stengel, Will Rogers, M. Taub, Mark Twain, Kerr L. White, etc. Approaches to Preservation Storage Technologies 2
  • Collaborators & Co-Conspirators • Jefferson Bailey, Karen Cariani, Jonathan Crabtree, Michelle Gallinger, Jane Mandelbaum, Nancy McGovern Trevor Owens • NDSA Coordination Committee & Working Group Chairs • Research Support Thanks to the Library of Congress, & the Massachusetts Institute of Technology. Approaches to Preservation Storage Technologies 3
  • Related Work • Altman, et. al, 2013. “NDSA Storage Report: Reflections on National Digital Stewardship Alliance Member Approaches to Preservation Storage Technologies”, Dlib 19 (5/6) • National Digital Stewardship Alliance, 2013 (Forthcoming), 2014 National Agenda for Digital Stewardship. • Micah Altman, Jonathan Crabtree (2011) Using the SafeArchive System : TRAC-Based Auditing of LOCKSS, 165-170. In Archiving 2011. Most reprints available from: informatics.mit.edu Approaches to Preservation Storage Technologies 4
  • Simple question? • If you have 1000 files (bitstreams), and you’d like to have 99.99% chance of accessing them in 20 years. How do you store them? Approaches to Preservation Storage Technologies 5
  • Simplistic Answer: Put it in AWS • Amazon Glacier claims a design reliability of 99.999999999% • Neat-o !!!!!!!!!! – Longer odds than winning Powerball OR – Getting struck by a lightning, three times OR – (Possibly) eventually finding alien civilization • But … Approaches to Preservation Storage Technologies 6
  • Clarifying Requirements • What are the units of reliability? - Collection? Object? Bit? • What is the natural unit of risk? • Is value of information uniform across units? • How many of these do you have? Approaches to Preservation Storage Technologies 7
  • Hidden Assumptions • Reliability estimates appear entirely theoretical – (MTBF + Independence)* enough replicas -> as many 9’s as you like… – No details for estimate provided – No historical reliability statistics provided – No service reliability auditing provided • Empirical Issues – Storage manufacture hardware MTBF (mean time between failures) does not match observed error rates in real environments… – Failures across hardware replicas are observed to correlated • Unmodeled failure modes – software failure (e.g. a bug in the AWS software for its control backplane might result in permanent loss that would go undetected for a substantial time_ – legal threats (leading to account lock-out — such as this, deletion, or content removal); – institutional threats (such as a change in Amazon’s business model) – Process threats (someone hits the delete button by mistake; forgets to pay the bill; or AWS rejects the payment) Approaches to Preservation Storage Technologies 8
  • Business Risks? • Amazon SLA’s do not incorporate or reflect “design” reliability claims: – No claim to reliability in SLA’s – Sole recover for breach limited to refund of fees for periods the service was unavailable – No right to audit logs, or other evidence of reliability Approaches to Preservation Storage Technologies 9
  • What practices are leading stewardhip organizations using? Approaches to Preservation Storage Technologies 10
  • Results from the NDSA Bi-Annual Preservation Storage Survey • 74 institutions surveyed. 58 met selection criteria. – Follow up on non-responders: 100% response rate. – Low rolloff on individual questions – Next round will be > 2x bigger • Survey Methods – Close ended, with open ended extensions – Selected qualitative followup • Survey Data – Instrument and data available as open data Approaches to Preservation Storage Technologies 11
  • About the NDSA Approaches to Preservation Storage Technologies 12
  • Key Findings: What are Current Institutional Practices? • 90% of respondents are distributing copies of at least part of their content geographically • 88% of respondents are responsible for their content for an indefinite period of time • 80% of respondents use some form of fixity checking for their content • 75% of respondents report a strong preference to host and control their own technical infrastructure for preservation storage • 69% of respondents are considering or currently participating in a distributed storage cooperative or system (ex. LOCKSS alliance, MetaArchive, Data-PASS) • 64% of respondents are planning to make significant changes in the technologies in their preservation storage architecture in the next three years • 51% of respondents are considering or already using a cloud storage provider to keep one or more copies of their content • 48% of respondents are considering, or currently contracting out storage services to be managed by another organization or company Approaches to Preservation Storage Technologies 13
  • How Many Copies Approaches to Preservation Storage Technologies 14
  • How Many Copies? … by Role Approaches to Preservation Storage Technologies 15
  • Preservation Storage -- New Approaches Approaches to Preservation Storage Technologies 16
  • What do organizations want from their preservation systems? Approaches to Preservation Storage Technologies 17
  • What are most memory organizations not doing yet? • Formal cost and valuation models • Auditing&evaluation • Certification • Comprehensive content review Approaches to Preservation Storage Technologies 18
  • Plans for future Approaches to Preservation Storage Technologies 19
  • Emerging State of the Practice Approaches to Preservation Storage Technologies 20
  • Methods for Mitigating Bit-Level Risk Physical: Media, Hardware, Environment Number of copies Diversification of copies Formats File Transforms: compression, encoding, encryption Fixity Repair Local Storage File Systems: transforms, deduplication, redundancy Replication Verification Audit Approaches to Preservation Storage Technologies 21
  • Emerging State of Practice • Organizational – Multi Institutional Stewardship – Institutions hold digital assets they wish to preserve, many unique – Many of these assets are not replicated at all – Even when institutions keep multiple backups offsite, many single points of failure remain, because replicas are managed by single institution – Approaches: LOCKSS, Digital Preservation Network, MetaArchive, Data-PASS, Datanet Federation Consortium, Data-ONE • Technical: Fixity, verification and auditing • Legal: Secession planning, Confidentiality, … Approaches to Preservation Storage Technologies 22
  • Future research: What do we need to know? Approaches to Preservation Storage Technologies 23
  • Modeling Bit Corruption Media characteristics Threat characteristics Correlations Logical Scope of Corruption File Characteristics File system Characteristics Probability of Successful Repair Auditing Frequency Number of copies Repair frequency Corruption Detection Repair Approaches to Preservation Storage Technologies 24
  • The Risk Problem Restated Keeping risk of object loss fixed -- what choices minimize $? “Dual problem” Keeping $ fixed, what choices minimize risk? Extension For specific cost functions for loss of object: Loss(object_i), of all lost objects What choices minimize: Total cost= preservation cost+ sum(E(Loss)) risk cost Are we there yet? Approaches to Preservation Storage Technologies 25
  • Research Directions • Growing the evidence base – Descriptive inference – patterns of use – Descriptive inference – outcomes – Predictive inference – trend analysis – Causal inference – effectiveness of interventions • Modes of inquiry – probability-based surveys (e.g. of information management practice and outcomes) – replicable simulation experiments tied to theoretically grounded models of information management and risk; – creation of testbeds and test-corpuses which can be used to systematically compare new practices, tools, and methods; – field experiments, in which randomized interventions are applied and evaluated in real operational environments. Approaches to Preservation Storage Technologies 26
  • Bibliography (Selected) • David S.H. Rosenthal, Thomas S. Robertson, Tom Lipkis, Vicky Reich, Seth Morabito. “Requirements for Digital Preservation Systems: A Bottom-Up Approach”, D-Lib Magazine, vol. 11, no. 11, November 2005. • Pinheiro, E., Weber, W.D., & Barroso, L. A. (2007). Failure trends in a large disk drive population. In Proceedings of 5th USENIX Conference on File and Storage Technologies. • Rosenthal, David SH. "Bit preservation: a solved problem?." International Journal of Digital Curation 5.1 (2010): 134-148. Approaches to Preservation Storage Technologies 27
  • Questions? E-mail: escience@mit.edu Web: micahaltman.com Twitter: @drmaltman Approaches to Preservation Storage Technologies 28