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Section 13.2 – Secondary storage managament. Index. 13.2 Disks 13.2.1 Mechanics of Disks 13.2.2 The Disk Controller 13.2.3 Disk Access Characteristics. Mechanics of Disks. 2 principal moving pieces of hard drive 1- Head Assembly 2- Disk Assembly
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Index • 13.2 Disks • 13.2.1 Mechanics of Disks • 13.2.2 The Disk Controller • 13.2.3 Disk Access Characteristics
Mechanics of Disks • 2 principal moving pieces of hard drive 1- Head Assembly 2- Disk Assembly • Disk Assembly has 1 or more circular platters that rotate around a central spindle. • Platters are covered with thin magnetic material
Tracks are concentric circles on a platter. • Tracks are organized into sectors which are segments of circular platter. • Sectors are indivisible as far as errors are concerned. • Blocks are logical data transfer units.
Disk Controller • Control the actuator to move head assembly • Selecting the surface from which to read or write • Transfer bits to main memory
Disk Storage characteristics • Rotation speed • Number of platters per unit • Number of tracks per surface • Number of bytes per track
Disk Access characteristics • Seek time • Rotational latency • Transfer time
Writing blocks almost same as reading blocks • For modifying , blocks need to be loaded into main memory and re-written to disk.