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Fast Guide: Storage technologies

By 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
• For the enterprise

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