Advanced Operating Systems   COMP9242 2002/S2

UNSW

Printer-Friendly Version Administration                - Notices - Course Intro - Consultations # On-line Survey (closed) - Survey Results   Work - Lectures - Milestone 0 - Project Admin - Project Spec - Project FAQ - Exam   Documentation - ASysT Lab - L4 source browser - Sulima ISA Simulator - R4x00 ISA Summary  - MIPS R4700 Reference - MIPS R4000 User Manual  - Network Driver - GT64111   Related Info - Aurema OS Prize - OS Hall of Fame   History - 2000 - 1999 - 1998   Staff - Gernot Heiser (LiC)

The Original Unix File System (UFS) First block on disk is Boot block read by firmware for booting Second block of disc is superblock: disk geometry, incl. total number of blocks, pointer to block free list. Next is inode array, containing pointers to disk blocks. Finally data blocks. New things Flat files -- just a string of bytes Structure imposed by user and convention Directories maintained by OS, just name $\Leftrightarrow$ inumber namei() got expensive... Physical volumes could be Mounted into hierarchical namespace As discs got larger this was extended to: Volume table-of-contents (VTOC) at start of disk, Several partitions per physical disk. Each partition can contain a file system. Partitions can be mounted into hierarchical namespace. UFS problems: Small block size (512b). Easily fixed: Doubling doubled performance. No redundancy, hence easy to destroy. Loss of superblock is disaster. No locality: Inodes and data in different parts of disk. Block allocation using free list leads to randomisation of file's blocks. Generally no attempt to minimise rotational and seek latencies.