Comparing Secondary Storage / Computers

Magnetic Storage

Hard Disc Drive

Components: electric motor, Circuit board, actuator arms and heads, disc platters.Electricity and magnetism drive arms across disc at lightning speed

Data: The data is stored inside disc surface as bytes. There are 31 billion bytes in ea. sq. cm. of the disc’s surface

Flash Storage

Solid-State Drives (SSD), Memory Sticks, USB Drives

In Flash memory electrons are stored in a permanent or non-volatile way. There are no moving parts larger than electrons. The computer reads the electrons.

Optical Storage

Includes CD's, DVDs, video games, music CDs

The computer reads the bumps or bytes on the disc’s surface. The bumps are a binary series of 1s and 0s.


As of 2015, the primary competing technology for secondary storage is flash memory in the form of solid-state drives over hard disc drives (still the inexpensive workhorse of storage). One advantage of the SSD is that there are no moving parts other than electrons and they are non-volatile.  Flash storage is quiet and not as affected by being moved about or accidentally bumped or dropped. They are inherently faster.

A downside of Flash Memory is that it costs more per unit of storage.

Cost Analysis: HDD $0.05-0.08/gigabyte; SSD $0.60/gig; blank CD $0.25/gig; USB flash drive $1.50-$4.00/gig; external HD $0.18/gig

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