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Definition of "Persistent data"

"Persistent data" are all data stored in a non-volatile storage such as a hard disk drive or FLASH memory.

Here follows a more detailed definition of different types of data which is in a persistent storage and survive a power down cycle:

  • Program code
    • Non updated code (bootstrap)
    • updated code by OEM
    • program partial updates by end-user (backup of original code)
  • Data
    • Write once, cannot be updated in the field (in tier 1 factory, e.g. calibration, serial number, ...)
    • Write via diagnostics (in OEM factory or service, e.g. coding, VIN, ...)
    • Security related (in tier 1 or OEM factory or service e.g., secret keys/password for encryption/authentication)
    • Program code related data (in the field by service or customer, e.g. navigation maps, splash screen, ...)
    • Customer data per user generated by the user (in the field by customer, e.g. mp3, picture, phone book, PIM, ...)
    • User configuration data per user generated by applications; might be imported/exported (in the field, e.g. LUM, personal settings, ...)

Note on proposed storage:

  • MTD Mapped means: in a memory partition that most probably will be on raw FLASH (see [SysInfraEGPersistenceFlashFS])
  • Read only FS means: in a simple and very fast File System as CRAMFS that could be updated rewriting the whole partition
  • Special FS means: a file systems robust against power loss (e.g., UBI-FS)
  • Generic FS means: whatever file systems that has not to be robust against power loss (e.g., a FAT USB Mass storage)
  • Persistence client library (clientLib)

Starting from data definition above a more detailed table follows:

Persistence ScopeData typeAvailabilityProposed storageRead SpeedWrite SpeedCapacityData
cachedcan be delayedfrequencyread onlyneeds
error detection / correction (recovery)signatureEG that is
covering it
Data provided by
 Non updated code (bootstrap)boot loaderMTD mappedfastdon't carekiloyesnoyesfactoryyesnononoyesTBD 
 updated application code by OEMkernelSpecial flash FSfastfastmegayesnoyesdiagnosticyesnonodetectyesAutomotive 
ExtendedSecurity related databoot loaderMTD mappeddon't caredon't carekiloyesnoyesfactory / disgnosticyesnonocorrectnoSysInfra 
ExtendedEncrypted dataruntimeSpecial flash FSfastfastkiloyesnoyesseldomnononodetectyesSysInfra 
 program partial updates by end-userinitSpecial flash FSfastdon't caremegayesnonoseldomnoyesyesdetectyes  
ExtendedData write once, cannot be updated in the fieldboot loaderMTD mappeddon't caredon't carekiloyesnonofactoryyesnonocorrectnoSysInfra 
ExtendedData write via diagnosticsboot loaderMTD mappedfastas fast as possiblekiloyesnonodiagnosticnononodetectyesSysInfra 
CurrentApplication program code related datainitSpecial flash FS clientLibfastas fast as possiblemeganoyesyesseldomnonoyesdetectnoSysInfra 
CurrentSystem Program code related databoot loaderSpecial flash FS clientLibfastas fast as possiblekilonononoseldomnonoyescorrectnoSysInfra 
CurrentCustomer data per user generated by the userruntimeGeneric FS clientLibas fast as possibleas fast as possiblemeganoyesyesseldomnononodetectnoSysInfra 
CurrentUser configuration data per user generated by applicationsboot loaderclientLibfasttime criticalkilonononooftennoyesyesdetectnoSysInfra 


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Last Edit: 11:51, 18 August 2014‎ Ingo.Huerner

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