A data storage device is a device for recording (storing) information (data). Recording can be done using virtually any form of energy. People have been storing data for thousands of years, by pictures and writing. Modern storage device may hold information, process information, or both. Most often the term is used with computers. Data storage devices can permanently hold data, like files.

Electronic data storage is storage which requires electricity to store and get back that data. Most storage devices that do not require visual optics to read data fall into this category.  Electronic data may be stored in either an analog or digital signal format.

Terminology
An organic brain may or may not be considered a data storage device.

All information is data. However, not all data is information.

Data storage equipment
Any input/output equipment may be considered data storage equipment if it writes to and reads from a data storage medium. Data storage equipment uses either:
 portable methods (easily replaced),
 semi-portable methods requiring mechanical disassembly tools and/or opening a chassis, or
 inseparable methods meaning loss of memory if disconnected from the unit.
The following are examples of those methods:

Portable methods 
Hand crafting
Flat surface
Printmaking
Photographic
 Fabrication
Textile
 Cylindrical accessing
 Memory card reader/drive
 Tape drive
Mono reel or reel-to-reel
Compact Cassette player/recorder
 Disk accessing
Disk drive
Floppy disk
 Cartridge accessing/connecting (tape/disk/circuitry)
 Peripheral networking
 Flash memory devices

Semi-portable methods 
 Hard disk drive
 non-volatile RAM

Inseparable methods 
 Volatile RAM
 Neurons

Recording medium
A recording medium is a physical material that holds data expressed in any of the existing recording formats. With electronic media, the data and the recording medium is sometimes referred to as "software" despite the more common use of the word to describe computer software.

Ancient and timeless examples

 Optical
 Any object visible to the eye, used to mark a location such as a, stone, flag or skull.
 Any crafting material used to form shapes such as clay, wood, metal, glass, wax.
 Quipu
 Any branding surface that would scar under intense heat (chiefly for livestock or humans).
 Any marking substance such as paint, ink or chalk.
 Any item that would hold a marking substance such as, papyrus, paper, skin.
 Chemical
 RNA
 DNA
 Pheromone

Modern examples by energy used

Chemical
Dipstick
Thermodynamic
Thermometer
Photochemical
Photographic film
 Mechanical
Pins and holes
 Punch card
 Paper tape
Music roll
 Music box cylinder or disk
Grooves  (See also Audio Data)
 Phonograph cylinder
 Gramophone record
 DictaBelt (groove on plastic belt)
 Capacitance Electronic Disc
Magnetic storage
Wire recording (stainless steel wire)
Magnetic tape
Drum memory (magnetic drum)
Floppy disk
Optical storage
 Photo paper
 X-ray
 Hologram
 Projected transparency
 Optical disc
 Magneto-optical disc
 Holographic versatile disc
 3D optical data storage
Electrical
Semiconductor used in volatile RAM microchips
Floating-gate transistor used in  non-volatile memory cards

Modern examples by shape
A typical way to classify data storage media is to consider its shape and type of movement (or non-movement) relative to the read/write device(s) of the storage apparatus as listed:
 Paper card storage
 Punched card (mechanical)
 Tape storage (long, thin, flexible, linearly moving bands)
 Paper tape (mechanical)
 Magnetic tape (a tape passing one or more read/write/erase heads)
 Disk storage (flat, round, rotating object)
 Gramophone record (used for distributing some 1980s home computer programs) (mechanical)
 Floppy disk, ZIP disk (removable) (magnetic)
 Holographic
 Optical disc such as CD, DVD, Blu-ray Disc
 Minidisc
 Hard disk drive (magnetic)
 Magnetic bubble memory
 Flash memory/memory card (solid state semiconductor memory)
 xD-Picture Card
 MultiMediaCard
 USB flash drive (also known as a "thumb drive" or "keydrive")
 SmartMedia
 CompactFlash I and II
 Secure Digital
 Sony Memory Stick (Std/Duo/PRO/MagicGate versions)
 Solid-state drive

Related pages
Archive
Computer data storage
Data vault
Library
Multimedia

References
Bekenstein, Jacob D. (2003, August). Information in the holographic universe. Scientific American.

Bibliography

Other websites
Historical Notes about the Cost of Hard Drive Storage Space