Lec20 - Today: Distributed File Systems Overview of...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
CS677: Distributed OS Computer Science Lecture 20, page Today: Distributed File Systems Overview of stand-alone (UNIX) file systems Issues in distributed file systems Next two classes: case studies of distributed file systems NFS Coda xFS Log-structured file systems (time permitting) 1 CS677: Distributed OS Computer Science Lecture 20, page File System Basics File: named collection of logically related data Unix file: an uninterpreted sequence of bytes File system: Provides a logical view of data and storage functions User-friendly interface Provides facility to create, modify, organize, and delete files Provides sharing among users in a controlled manner Provides protection 2
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CS677: Distributed OS Computer Science Lecture 20, page Unix File System Review User file: linear array of bytes. No records, no file types Directory: special file not directly writable by user File structure: directed acyclic graph [directories may not be shared, files may be shared (why?) ] Directory entry for each file File name inode number Major device number Minor device number All inodes are stored at a special location on disk [super block] Inodes store file attributes and a multi-level index that has a list of disk block locations for the file 3 CS677: Distributed OS Computer Science Lecture 20, page Inode Structure Fields Mode Owner_ID, group_id Dir_file Protection bits Last access time, last write time, last inode time Size, no of blocks Ref_cnt Address[0], … address[14] Multi-level index: 12 direct blocks, one single, double, and triple indirect blocks 4
Background image of page 2
Computer Science Lecture 20, page Distributed File Systems File service: specification of what the file system offers Client primitives, application programming interface (API) File server: process that implements file service Can have several servers on one machine (UNIX, DOS,…) Components of interest File service Directory service 5 CS677: Distributed OS Computer Science Lecture 20, page File Service Remote access model Work done at the server Stateful server (e.g., databases) Consistent sharing (+) Server may be a bottleneck (-) Need for communication (-) Upload/download mode
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 13

Lec20 - Today: Distributed File Systems Overview of...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online