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School of Computer Science & Engineering
University of New South Wales
 Advanced Operating Systems 
 COMP9242 2002/S2 

Alternative:
Logging to Improve Throughput

• Based on write-ahead logging used by databases.
• Maintain an append-only redo-log for metadata updates.
• Cedar[Hag87]:
  • Log written twice a second, grouping metadata updates.
  • Must ensure that log records are written before the logged metadata.
  • Other updates can be undone if crash before log write.
  • Use B-tree for directories.
  • Keep other metadata just before first data block.
• Linux ext3