Computer Science 432 Operating Systems Williams College Fall 2006

Agenda

• Announcements
  • CS Colloquium this week: Tim Huang, Middlebury College, Title: "Beyond Deep Blue: Advances in Computer Go"
  • Submit final project progress reports before Thanksgiving break.
• Lecture assignment recap
• File Systems
  • More on Unix Inodes
  • Free Space Management
    • bit vector
    • free list
  • Caching
    • disks are slow, we want to use caching to speed up
    • caches may be in main memory, disk controller, disk drive
    • many Unix systems use: buffer cache
    • this introduces potential inconsistencies, need consistency checkers like fsck, scandisk
  • Log-based/Journaled File Systems
    • avoid inconsistencies by writing changes to the filesystem as atomic transactions
    • state of file system is determined by actual file system on disk and a set of uncommitted transactions
    • approach also provides performance benefits
  • RAID: a file system spanning multiple disks/partitions
    • Redundant Array of Independent/Inexpensive Disks
    • store a partition across multiple disks
    • improve reliability
    • improve efficiency
    • convenience
    • RAID levels: 0 through 6, 0+1, 1+0
    • implementation in software or hardware

Lecture Assignment

Due at the start of class, Tuesday, November 21.

Turn in short answers to these questions. Please turn in a hard copy (typeset or handwritten are OK). We will discuss these questions during class, so no late submissions are accepted.

SG&G 12.8, 12.9

The readings for next time are SG&G Chapter 13.

Examples