ch13-Disk Storage, Basic File Structures, and Hashing

ch13-Disk Storage, Basic File Structures, and Hashing -...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
Slide 13- 1 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe
Background image of page 1

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

View Full DocumentRight Arrow Icon
Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Chapter 13 Disk Storage, Basic File Structures, and Hashing
Background image of page 2
Slide 13- 3 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Chapter Outline Disk Storage Devices Files of Records Operations on Files Unordered Files Ordered Files Hashed Files Dynamic and Extendible Hashing Techniques RAID Technology
Background image of page 3

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

View Full DocumentRight Arrow Icon
Slide 13- 4 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Disk Storage Devices Preferred secondary storage device for high storage capacity and low cost. Data stored as magnetized areas on magnetic disk surfaces. A disk pack contains several magnetic disks connected to a rotating spindle. Disks are divided into concentric circular tracks on each disk surface . Track capacities vary typically from 4 to 50 Kbytes or more
Background image of page 4
Slide 13- 5 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Disk Storage Devices (contd.) A track is divided into smaller blocks or sectors because it usually contains a large amount of information The division of a track into sectors is hard-coded on the disk surface and cannot be changed. One type of sector organization calls a portion of a track that subtends a fixed angle at the center as a sector. A track is divided into blocks . The block size B is fixed for each system. Typical block sizes range from B=512 bytes to B=4096 bytes. Whole blocks are transferred between disk and main memory for processing.
Background image of page 5

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

View Full DocumentRight Arrow Icon
Slide 13- 6 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Disk Storage Devices (contd.)
Background image of page 6
Slide 13- 7 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Disk Storage Devices (contd.) A read-write head moves to the track that contains the block to be transferred. Disk rotation moves the block under the read-write head for reading or writing. A physical disk block (hardware) address consists of: a cylinder number (imaginary collection of tracks of same radius from all recorded surfaces) the track number or surface number (within the cylinder) and block number (within track). Reading or writing a disk block is time consuming because of the seek time s and rotational delay (latency) rd . Double buffering can be used to speed up the transfer of contiguous disk blocks.
Background image of page 7

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

View Full DocumentRight Arrow Icon
Slide 13- 8 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Disk Storage Devices (contd.)
Background image of page 8
Slide 13- 9 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Typical Disk Parameters (Courtesy of Seagate Technology)
Background image of page 9

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

View Full DocumentRight Arrow Icon
Slide 13- 10 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Records Fixed and variable length records Records contain fields which have values of a particular type E.g., amount, date, time, age Fields themselves may be fixed length or variable length Variable length fields can be mixed into one record: Separator characters or length fields are needed so that the record can be “parsed.”
Background image of page 10
Slide 13- 11 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Blocking
Background image of page 11

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

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/23/2012 for the course CS 348 taught by Professor Staff during the Fall '08 term at Purdue University-West Lafayette.

Page1 / 35

ch13-Disk Storage, Basic File Structures, and Hashing -...

This preview shows document pages 1 - 12. Sign up to view the full document.

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