Segment Cleaning

• How to identify file that a block belongs to?

• How to identify live blocks?

• LFS solution: segment summary block

  • maps data blocks to file-id+block-id
  • version number: identifies live blocks
    • updated on overwrite or delete
  • version number + inode number = uid

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to check whether a block is live or not:

look into file’s inode or indirect block and see if this block is in it.

FFS: free block list or bitmap.

Saves disk space and memory