67. The $Quota

• Located in $Extend directory (on Windows NT was inode #9)

• Tracks how much space on the volume is allocated by every user.

• Contains two indexes:

  • $O contains an entry for everyone that has a quota enforced on them.

  • $Q has an entry for every user login on the system.

• When a file is accessed,

  1. A lookup is done in $O for the file owner to see if they have a quota

  2. A lookup is done in $Q to see what the quota is.