News Analysis

Fast Guide: Storage technologies

Whatis and SearchStorage.com editorial
Because storage technologies and their terms are somewhat different for the personal or small business computer user than for the enterprise user, we've divided this guide into two parts. To the extent that some technologies depend on other technologies (for example, a storage area network depends on either Fibre Channel or iSCSI for its connection protocol), there is a certain amount of redundancy among some table entries.

For individuals and small businesses

Technology
  • Advantages
  • Limitations
  • Applications
Compact disc, recordable
( CD-R ) or rewritable ( CD-RW ) and DVD
  • Low cost per Mbyte
  • Unlimited capacity with multiple discs
  • Portable
  • Widely-supported I/O interfaces
  • Can be formatted for different data formats
  • Long life
  • High data density
  • Immune to corruption once data is written (CD-R and DVD only)
  • Limited capacity on one disc (though much greater than diskette)
  • Slow to moderate read/write speed
  • Data archiving
  • Data distribution
  • Data migration
  • Localised file sharing
  • Offsite storage
Diskettes, 1.44 MB
  • Simple to use
  • Portable
  • Can be formatted for different data formats
  • Limited capacity
  • Limited read/write speed
  • Not supported by many newer computers
  • Local data transfer of small files
  • Storage of small files or programs
Hard drive, external
  • High read/write speed
  • Can be moved among computers
  • Limited capacity
  • Awkward for data transfer among multiple computers
  • Local backup
  • Local archiving
Hard drive, internal
  • Convenient; usually comes with the computer
  • High read/write speed
  • Convenient for use with single computer (but can be shared among multiple computers with proper support
  • Most common form of data storage
  • Limited capacity
  • Without special support, confined to a single computer or server
  • Storage in a single computer
  • Swap files
Removable storage (ZIP disks, JAZ discs, etc.)
  • Simplicity
  • Portability
  • Unlimited capacity with multiple discs
  • Convenient for use with single computer
  • Proprietary media
  • Limited read/write speed
  • High cost per Mbyte
  • Personal computing
  • Local data transfer of small files
  • Local backup
  • Local archiving
Solid-state storage (USB devices, flash memory, smart cards, etc.)
  • No mechanical parts
  • High read/write speed
  • Small form factor
  • Limited storage capacity
  • High cost per I/O operation
  • Swap files
  • Local data transfer
  • Internet service providers
  • Video processing
  • Relational databases
  • High-speed data acquisition

For the enterprise (in addition to the above)

Technology
  • Advantages
  • Limitations
  • Applications
Direct-attached storage (DAS)
  • Simplicity
  • Low initial cost
  • Ease of management
  • Storage for each server must be administered separately
  • Inconvenient for data transfer in network environments
  • Server bears load of processing applications
  • Data and application sharing
  • Data backup
  • Data archiving
    Disc library
    • High speed
    • High storage capacity
    • High data availability
    • Disc-to-disc (D2D) backup
    • Data archiving
    • Near line storage
    Disc-to-disc-to-tape ( D2D2T )
    • Redundancy
    • High read/write speed
    • Unlimited capacity with multiple tapes
    • Complexity
    • Incremental backups
    • Storage virtualisation
    • Offsite storage
    • Data archiving
    Fibre Channel
    (See Storage area network below)
    • Used to transmit data between devices at gigabit speeds
    • Frequently used in storage area networks ( Sans)
    • Flexible in terms of distance
    • High cost
    • Management complexity
    • Large databases
    • Bandwidth-intensive applications
    • Storage area networks (Sans)
    • Offsite storage
    • Mission-critical applications
    iSCSI
    (See Storage area network below)
    • Used to transmit data between devices using the Internet Protocol ( IP )
    • Frequently used in storage area networks ( Sans)
    • More flexible in terms of distance than Fibre Channel (but not as fast)
    • May not compare favourably with Fibre Channel for large database transfers
    • Management complexity
    • Applications involving remotely distributed databases
    • Storage area networks (Sans)
    • Offsite storage
    • Mission-critical applications
    Magnetic tape
    • Low cost per Mbyte
    • Portability
    • Unlimited capacity with multiple tapes
    • Inconvenient for quick recovery of individual files or groups of files
    • Data archiving
    • Limited-budget businesses
    • Offsite storage
    Network-attached storage (Nas)
    • Fast file access for multiple clients
    • Ease of data sharing
    • High storage capacity
    • Redundancy
    • Ease of drive mirroring
    • Consolidation of resources
    • Less convenient than storage area network (San) for moving large blocks of data
    • Data backup
    • Data archiving
    • Redundant storage
    Redundant array of independent discs (RAID)
    • High speed
    • High storage capacity
    • High data availability
    • High reliability
    • Security
    • Fault tolerance
    • Users may develop false sense of security
    • Recovery from failure is difficult in some systems
    • High cost for optimum systems
    • Swap files
    • Internet service providers
    • Redundant storage
    Storage area network (SAN)
    • Excellent for moving large blocks of data
    • Exceptional reliability
    • Wide availability
    • Fault tolerance
    • Scalability
    • High cost
    • Lack of standardization
    • Management complexity
    • Large databases
    • Bandwidth-intensive applications
    • Mission-critical applications

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