Storage Abstractions in TinyOS 2.x

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Storage Abstractionsin TinyOS 2.x

• Jonathan Hui
• jwhui_at_cs.berkeley.edu
• University of California, Berkeley

David Gay dgay_at_acm.org Intel Research, Berkeley
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Non-Volatile Storage

• Flash storage becoming more widely used
• Mass data storage
• logging sensor data
• network programming
• event logging for debugging
• Configuration data that survives
• power-failure
• reprogramming

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Flash Storage Variety

• STMicro M25P (NOR)
• Telos rev. B, Eyes 1
• Intel StrataFlash (NOR)
• iMote 2
• Atmel AT45DB (NOR)
• Mica Family, Telos rev. A, Eyes 2
• But has very different characteristics

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Technology Differences

• One write per bit per erase cycle
• Flash characteristics

Not used in current motes
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Architecture

• Differences limited RAM preclude common
  low-level HIL interfaces (e.g. block interface)
• Provide high-level storage services useful for
  sensor network applications
• Large Objects
• Small Objects
• Large Sequential Objects
• Separate implementations of these abstractions
  for each class of storage chip

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Large Objects

• Get a large object, write to each byte once in
  any arbitrary order, and commit.
• Characteristics
• Size Large (100B to 100KB, or more)
• Reads random
• Writes random (write once)
• Fault tolerance validity check
• Example Applications
• Network Programming
• Large Data Transfer

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Small Objects

• Maintain a small chunk of values. Requires
  multiple and random reads/writes.
• Characteristics
• Size Small (lt 100B)
• Reads random
• Writes random
• Fault tolerance writes are atomic
• Failure between/during writes ? no data loss
• Example Applications
• Configuration data storage

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Large Sequential Object

• Some applications (e.g., low-rate data
  collection) may want to reliably log all their
  results.
• Characteristics
• Size Large
• Reads sequential
• Writes sequential
• Fault tolerance user-specified commit points
• Failure between/during writes ? entire object is
  not lost
• Example Applications
• Logging

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Putting It Together

• Sharing the flash through Volumes, with numerical
  identifiers
• Volumes allocated similar to using fdisk.
• A utility explicitly formats the flash.
• 1) Init volume table
• 2) Allocate each desired volume (user specifies
  UID and size)
• 3) Commit volume table
• Volume table kept in non-volatile storage.

Volume 0
Volume 1
Volume 2
Volume 3
Flash
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Putting It Together

• TinyOS apps must mount volume before use.
• Mount by specifying UID of volume
• No unmount operation
• A volume is used by at most one HIL.
• Allows switching of applications while managing
  the sharing of flash.

Small Object
Large Object
Log
Log
Volume 0
Volume 1
Volume 2
Volume 3
Flash
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Implementation Status

• Currently under development
• AT45DB Mica family, Telos rev. A, Eyes 2
• STM25P Telos rev. B, Eyes 1
• Alpha (incomplete, etc) code on SourceForge, in
• tinyos-2.x/tos/chips/at45db
• tinyos-2.x/tos/chips/stm25p
• Thanks!

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Backup Slides
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BlockStorage

• interface BlockRead
• command result_t read(addr_t addr, void dest,
  addr_t len)
• event void readDone(storage_result_t result)
• command result_t verify()
• event void verifyDone(storage_result_t result)
  
• interface BlockWrite
• command result_t write(addr_t addr, void
  source, addr_t len)
• event void writeDone(storage_result_t result)
• command result_t erase()
• event void eraseDone(storage_result_t result)
• command result_t commit()
• event void commitDone(storage_result_t result)
  

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ConfigStorage

• interface ConfigStorage
• command result_t read(addr_t addr, void dest,
  addr_t len)
• event void readDone(storage_result_t result)
• command result_t write(addr_t addr void
  source, addr_t len)
• event void writeDone(storage_result_t result)
• command result_t commit()
• event void commitDone(storage_result_t result)
  

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Logger

• interface LogRead
• command result_t read(uint8_t data, uint32_t
  numBytes)
• event void readDone(uint8_t data, uint32_t
  numBytes,
• storage_result_t success)
• command result_t seek(uint32_t cookie)
• event void seekDone(storage_result_t success)
• interface LogWrite
• command result_t erase()
• event void eraseDone(storage_result_t success)
  
• command result_t append(uint8_t data, uint32_t
  numBytes)
• event void appendDone(uint8_t data, uint32_t
  numBytes,
• storage_result_t
  success)
• command uint32_t currentOffset()
• command result_t sync()
• event void syncDone(storage_result_t success)

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Volume Management

• interface FStorage
• command result_t init()
• command result_t allocate(uint8_t id, addr_t
  size)
• command result_t allocateFixed(uint8_t id,
  addr_t addr,
• addr_t size)
• command result_t commit()
• event void commitDone(storage_result_t result,
  uint8_t id)
• interface Mount
• command result_t mount(uint8_t id)
• event void mountDone(storage_result_t result,
  uint8_t id)