1 / 15

CS246 Data & File Structures Lecture 1 Introduction to File Systems

CS246 Data & File Structures Lecture 1 Introduction to File Systems. Instructor: Li Ma Office: NBC 126 Phone: (713) 313-7028 Email: malx@tsu.edu Webpage: http://itscience.tsu.edu/ma Department of Computer Science Texas Southern University, Houston. January, 2007. Motivation.

raven-parrish
Download Presentation

CS246 Data & File Structures Lecture 1 Introduction to File Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CS246 Data & File StructuresLecture 1 Introduction to File Systems Instructor: Li Ma Office: NBC 126 Phone: (713) 313-7028 Email: malx@tsu.edu Webpage: http://itscience.tsu.edu/ma Department of Computer Science Texas Southern University, Houston January, 2007

  2. Motivation • Why do we need file structure design? • What are most computers used to for? • Examples: • Editing document • Internet surfing or Composing email • Programming, etc. • Data processing: storage, organization, access, and operation on data by Li Ma, TSU - cs344

  3. Computer Architecture Main Memory Data is manipulated here Data Transfer Secondary Memory Data is stored here by Li Ma, TSU - cs344

  4. Advantages of Memories • Programs are executed in main memory since it is fast • Data is stored in secondary memories since • Data is not lost during power failures –stable • Affordable –large and cheap by Li Ma, TSU - cs344

  5. Disadvantages of Memories • Main memory is small and expensive • Many programs are too large to fit in main memory • Main memory is volatile, Data is lost during power failure • Secondary storage is slow (10,000 times slower than main memory) by Li Ma, TSU - cs344

  6. Solution • Secondary storage provides reliable, long-term storage for large volume of data • Data we are interested in (a small portion of data) is always in Main memory since it can be rapidly manipulated and processed • Data can be transferred automatically between the Main memory and the secondary storage by Li Ma, TSU - cs344

  7. Problem with the Approach • Transferring data between Main memory and secondary memory is slow because Secondary memory is slow • An important aspect of file system management is to minimize the amount of data transfer, or eliminate unnecessary transfers by Li Ma, TSU - cs344

  8. File Systems • Examples • Telephone book (primary index: name?) • Library (primary index: number, secondary indices: author, title, and subject) • A file system provides a convenient method for organizing and storing files by Li Ma, TSU - cs344

  9. File Systems (cont) • File systems are software programs that allow us to efficiently organize data and operate on data • Data is organized into files on hard disks or other physical media • A file is divided into records • Records are composed of fields by Li Ma, TSU - cs344

  10. Example of A File • A student file may be a collection of student records, one record for each student • Each student record may have several fields, such as: • Name • Address • Student Number • Sex • Age • Grade point average (GPA). by Li Ma, TSU - cs344

  11. Structure of A File • Typically, each record in a file has the same fields • Files are large and are stored in secondary storage • Records we are currently interested in are copied to Main memory • Organizing the records of a file, and getting the records we are interested in are the main topics of this course by Li Ma, TSU - cs344

  12. File Properties • Persistence: Data written into a file persists after the program stops, so the data can be used later • Sharability: Data stored in files can be shared by many programs and users simultaneously • Large Size: Data files can be very large that, typically, they cannot fit into Main memory by Li Ma, TSU - cs344

  13. File Structure Design • A file structure is a combination of representation for data in files and operations for accessing the data • The intension between a disk’s relatively slow access time and its enormous, non-volatile capacity is the driving force behind file structure design by Li Ma, TSU - cs344

  14. File Structures • Sequential file structures – files on tape • Indexed file structures – files on disk, with key and pointer • Tree structures: AVL tree, B-tree, B+ tree • Hash file re-organization by Li Ma, TSU - cs344

  15. Course Content & Outline • This course covers data processing from a computer science perspective: • Storage of data – storage devices (disk & tape) • Organization of data – file organization • sequential - Tape • direct (hashing) • indexed sequential (B-trees) • multi-key (secondary indices) • Access to Data – file systems • Processing of Data – database system by Li Ma, TSU - cs344

More Related