Sector layouts Disk Hardware Physical geometry of a disk with two zones (WD18300 has 16 zones) A possible virtual geometry for this disk (the controller Disk parameters for the original IBM PC floppy disk and does the mapping) a Western Digital WD 18300 hard disk 6/7/2001 1 6/7/2001 2 Audio CD and CD-ROM Logical data layout 600/mm 0.8micron 8-bit byte with bits for 5.6Km error correcting code 14*42 bits 192 bits 28% efficiency!! Laser beam reflection can differentiate 6/7/2001 between pits and lands (1’s and 0’s). 3 6/7/2001 4 1 CD-ROM characteristics CD-R (Recordable) Single-speed= 75 sectors/sec =153.6KB/sec Blank CD with a groove having sinusoidal 40x drive = 40*153.6KB/sec ~ 6MB/sec wave form ¡ Capacity = 650MB to guide the laser beam for writing ¡ Seek time ~ several hundred milliseconds 22.05KHz to monitor rotation speed (slow) ¢ Internal layer of transparent dye that can be Cost (blank) ~$1 burnt (to create dark spots) ¡ High power laser beam used to burn ¡ Low power laser beam used to read ¢ Incremental burning possible ¡ Kodak PhotoCD ¡ A new VTOC must be written 6/7/2001 5 6/7/2001 6 Reading a CD-R CD-RW (ReWritable) ¢ Dye is replaced by an alloy with two stable states ¡ Crystalline (high reflectivity) and Amorphous (low reflectivity) ¢ Laser has 3 power levels £ ¡ High power changes C A for recording ¤ Low power is used for reading £ ¤ Medium power changes A C for erasing ¥ CD-RW blanks are more expensive than CD-R blanks ¦ hasn’t caught on 6/7/2001 7 6/7/2001 8 2 A double sided, dual layer DVD disk Digital Video Disk (DVD) Differences from CD-ROM ¡ Has smaller pits (half as large as CD pits) ¡ Tighter spiral (twice as dense) ¡ Red laser has shorter wave length (higher resolution) Capacity=4.7GB (7 times) 1x drive =1.4MB/sec Can hold 133 minutes of high resolutions (720x480) video with sound tracks for 8 0.6mm languages (MPEG2) single-sided disk Official name is Digital Versatile Disk Can store 17GB! Official name=Digital Versatile Disk 6/7/2001 9 6/7/2001 10 Disk sector Disk Formatting 16 bytes Preamble: Special start-of-sector marker + sector number 6/7/2001 11 6/7/2001 An illustration of cylinder skew 12 3 Sector interleaving No interleaving Single interleaving Double interleaving 6/7/2001 13 4.