CHAPTER 8 = SECONDARY STORAGE

SECONDARY STORAGE 

•        Secondary storage devices are used to save, to back up, and even to transport files consisting of data or programs from one location or computer to another. 

•        Secondary storage devices have always been an indispensable element in any computer system.

•         Secondary storage provides permanent or nonvolatile storage.

•       Some important characteristics of secondary storage include:

1.     Media are actual physical material that holds the data and program.

2.     Capacity measure how much a particular storage medium can hold.

3.     Storage devices are hardware that reads data and programs from storage media.

4.     Access speed measure the amount of time required by the storage device to retrieve data and program. 

 

HARD DISKS

• A hard disk drive (HDD) is a non-volatile , random access device for digital data. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the platters. 

• Introduced by IBM in 1956, hard disk drives have fallen in cost and physical size over the years while dramatically increasing in capacity. Hard disk drives have been the dominant device for secondary storage of data in general purpose computer since the early 1960s. They have maintained this position because advances in their areal recording density have kept pace with the requirements for secondary storage. Today's HDDs operate on high-speed serial interfaces; i.e., serial ATA (SATA) or serial attached SCSI  (SAS).           

Components  

• A typical hard disk drive has two electric motors; a disk motor to spin the disks and an actuator (motor) to position the read/write head assembly across the spinning disks.

• The disk motor has an external rotor attached to the disks; the stator windings are fixed in place.   

• For more information refers to http://en.wikipedia.org/wiki/Hard_disk_drive     

INTERNAL HARD DISK   

• It is located inside the system units. 
• The are designated as C drive. 
• Are able to storage and retrieve large quantities of information quickly. 
• Used to storage program and large data files.                                                
    
   
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  EXTERNAL HARD DRIVE     
  • Provide fast access, they have a fixed amount of storage and cannot be easily removed from the system cabinet. 
  • Typically connect to a USB or FireWire port on the system unit, are easily removed and effectively provide an unlimited amount of storage. 
  • For desktop computers have typically capacities of 20 to 500 GB. 
  •   Credit card-size hard disks cartridges called PC Card hard disks are available for notebook computers with typically capacities up to 5 GB.

 

http://www.build-your-own-computer.net/external-hard-drive.html

Secondary storage are important because can be used to restore a backup of your files if you have to format. It also can be bring it with you if you need to access files at work or somewhere else. Without secondary storage you would lose all of you data every time your computer powered down. In order words , your computer would not have anywhere to save data indefinitely. For more information you can refers to http://wiki.answers.com/Q/Why_secondary_storage_devices_are _important.                                                                                                                            

Citation ~ http://wiki.answers.com/Q?Why_secondary_storage_devices_are_important.       

~http://en.wikipedia_org/wiki/Hard_disk_drive                                       

~Computing Essentials 2010 Books