7.1 Digital preservation techniques and best practices

Digital preservation is crucial for safeguarding rescued stories. It involves comprehensive strategies, from organizational policies to technological infrastructure. Key aspects include selecting appropriate file formats, implementing robust backup systems, and designing efficient digitization workflows.

Preserving digital content requires careful planning and execution. This includes choosing non-proprietary file formats, following the 3-2-1 backup rule, and creating detailed digitization workflows. Regular format migration and quality control are essential for long-term accessibility and integrity of digital archives.

Digital Preservation Strategies

Comprehensive Approach

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• A comprehensive digital preservation strategy addresses organizational infrastructure, technological infrastructure, and resources framework
• Key components include policies, staffing, selection, metadata, access, storage, security, disaster preparedness, and sustainability
• Policies should cover the scope of digital content preserved, retention schedules, access and use conditions, and preservation standards
  • Documented policies are essential for consistent implementation (retention schedules, use conditions)

Staffing and Resources

• Staffing and resourcing digital preservation requires defining roles and responsibilities, assessing current and future staffing needs, and budgeting for short and long-term requirements
• Selection criteria for digital preservation consider the information content, uniqueness, and value of the materials, as well as technical feasibility and sustainability
  • Not all content can or should be preserved (low-value, redundant content)
• Descriptive, administrative, structural, and preservation metadata are all critical to manage and preserve digital objects over time and maintain meaning, authenticity, and access

Storage and Security

• Storage and security include evaluating and implementing storage management systems and media that align with preservation policies and practices
• Multiple copies, geographical distribution, access controls, and security monitoring are best practices (offsite backup, encryption)
• Planning for sustainability and disaster preparedness requires risk assessment, succession planning, and established responses for a range of failure scenarios to ensure continuity of preservation

File Formats for Preservation

Selecting Preservation Formats

• Careful selection of file formats is critical for long-term preservation
• Formats should be non-proprietary, ubiquitous, and have freely available specifications (PDF/A, TIFF)
• Text-based formats like XML, PDF/A, and plain text are preferable to complex proprietary formats for documents
  • Markdown is suitable for simple documents
• For images, uncompressed TIFF is widely used for preservation
  • PNG, JPEG 2000, and PDF/A are other viable options

Evaluating Formats

• Recommended audio formats are uncompressed WAV, AIFF, or lossless compressed FLAC
• For video, uncompressed Quicktime or AVI and lossless JPEG 2000 are suitable
• Evaluating formats should consider the significant properties of the original that must be maintained, support for embedded metadata, error detection/correction, and compatibility with current and future systems
• Format registries like PRONOM provide detailed information about file formats to aid in evaluation and risk assessment over time
• A comprehensive preservation strategy may involve preserving the original bitstream alongside a normalized version in a preservation format
  • Multiple versions support different future use cases (access copy, preservation master)

Data Backup and Migration

Backup Strategies

• A 3-2-1 backup strategy is recommended - 3 total copies of the data, 2 on different media, and 1 copy kept offsite
  • Cloud storage can be leveraged for offsite copies (Amazon S3, Microsoft Azure)
• Backups should be automated where possible to ensure consistency and logged for verification
  • Backup frequency depends on data volatility and criticality (daily, weekly)
• Integrity of stored data should be ensured through the use of checksums and periodic validation
  • Bit-level preservation is crucial

Storage and Migration

• Storage media must be evaluated for underlying stability, vulnerability to degradation, and obsolescence
  • Migration to new storage media on a 3-5 year cycle is often necessary (magnetic tape to disk)
• Preservation storage systems must account for scalability as data volumes grow exponentially
  • Consider both maximum capacity and I/O performance
• Preservation repositories should conform to the ISO 14721 Open Archival Information System (OAIS) Reference Model for functionality and metadata requirements
• Format migration and emulation are two key strategies for ensuring long-term access
  • Migration converts data to new formats, while emulation recreates the original environment

Digitization Workflows

Workflow Design

• Digitization workflows should be designed to optimize efficiency, maintain quality control, and ensure consistency of practice
  • Workflows are highly dependent on material types and institutional requirements (maps, photographs, manuscripts)
• Key stages include selection, assessment, preparation, metadata collection, digitization, quality control, data storage, and access
  • Documenting each stage is essential
• Careful material handling and use of specialized equipment is necessary to avoid damaging fragile analog materials during digitization
  • Establish processes for stabilization and conservation (humidification, flattening, repair)

Parameters and Quality Control

• Digitization parameters and settings should be established based on material types and intended uses
  • Guidelines and recommendations are available from organizations like FADGI
• Quality control processes are critical to ensure completeness, accuracy, and consistency
  • Both manual and automated QC should be performed, assessing image quality, metadata, naming, formats, and fixity
• Workflows should generate and capture essential metadata, including descriptive, administrative, structural and preservation metadata
  • Metadata should be stored independently of the objects (sidecar files, databases)
• Fixity information like checksums should be generated and captured at the point of digitization and verified throughout the digitization chain of custody

Scalability and Sustainability

• Digitization workflows must be designed to scale and adapt to evolving technologies and standards over time
• Utilize open source tools where possible to avoid vendor lock-in (ImageMagick, Tesseract OCR)