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Secondary storage

Secondary storage is also known as backing storage

Speed is less important than large storage capability.

The most frequently used backing storage media are...

  • magnetic tape
  • magnetic disk
  • optical drives (CD-ROM ; DVD)
  • flash memory 
Magnetic Tape Commonly used for backup and archiving.  
Tape cartridge
(DLT or DAT Tape)		 DLT Possible 320 Gb of data on a single tape.
Maxell - Digital Audio Tape (DAT)

Magnetic Disk Fast storage and access to data.  
Floppy disk

 

 Portable...soon to only be found in museums!
Hard disk

  • Available in several sizes (500Gb is possible)
  • Permanently enclosed in their drive mechanism
  • Some drives are external and plug in to the USB port.

How do they work? - info here.

 Faster to store and load than floppy disk;

Sealed; Internal drives are not portable.
ZIP
Special ZIP drive needed. Up to 750 Mb on one disc.

A ZIP drive.

 Popularity is fading with the introduction of flash drives.
RAID Redundant Array of Inexpensive Drives. Used to improve reliability. A number of disks are used as one logical unit.

The idea is...if one disc crashes, no data is lost because it can be recreated from the other discs.

Increased reliability - so often used on file servers.

  

Optical Disks Laser technology is used to read data.  
CD-ROM

DVD

High capacity and portable.
  • Older CD standard stores up to 650 Mb
  • DVD stores up to 17 Gb

 
CD-R
DVD-R		 A CD-writer (or DVD writer) is needed to store data on a CD.  
CD-RW
DVD-RW

Rewritable CDs and DVDs can be used to record data many times.

Flash memory A flash memory chip stores the data  
USB Memory stick (USB Flash drive)

Portable storage media. It can be plugged into the USB port of any computer.

Typical storage...up to 8Gb

 
 

Memory sticks can be used in digital cameras to store pictures.