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   ► KBComputer TechHardwareNon-Removabl...   Print This     
  From the January 2016 Issue of Prestwood eMag
 
Non-Removable Storage Technology:
RAID
 
Posted 12 years ago on 1/21/2008 and updated 4/11/2010
Take Away:

RAID is the acronym for a Redundant Array of Independent Drives. RAID specifies several "levels," 0, 1, etc. Different levels provide different options. One level allows you to combine multiple smaller drives into one, huge volume. Another level offers tremendous performance boosts by "striping" data across multiple drives such that reads and writes are split across the drives. If one drive fails, the other takes over until the bad drive is replaced. Once replaced, the RAID subsystem automatically restores the mirror.

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KB100794

RAID -

RAID is the acronym for a Redundant Array of Independent Drives. RAID specifies several "levels," 0, 1, etc. Different levels provide different options. One level allows you to combine multiple smaller drives into one, huge volume. Another level offers tremendous performance boosts by "striping" data across multiple drives such that reads and writes are split across the drives. If one drive fails, the other takes over until the bad drive is replaced. Once replaced, the RAID subsystem automatically restores the mirror.


Tip: Once upon a time, RAID was used almost exclusively in servers. Nowadays, they are frequently used on workstations when the workstation contains valuable data (such as all your family photos). For a desktop machine, RAID Level 1 is indispensable. It provides drive "mirroring" in which a second drive is automatically maintained as a carbon copy of your primary drive.


RAID Level Description Pros Cons
0 Striping of data across multiple drives. Performance. Use all available HD space as if one drive. No redundancy.
1 Mirrored drives. Data duplicated on two drives. Read or write transaction performance. Redundancy. More expensive than RAID 0.
3 Data striped in bytes across multiple drives. Dedicated parity drive. High sustained data transfer rate. No performance degradation after drive failure. Redundancy. Lower performance with smaller random requests.
4 Data striped in blocks across multiple drives. Dedicated parity drive. High sustained data transfer rate. No performance degradation after drive failure. Redundancy. Lower performance with smaller random requests.
5 Data written in blocks across all drives; parity distributed among all drives. Good read performance with small, random I/O requests. Redundancy 50% performance loss with drive failure. Poor large request and write performance.

 

More Info

Blog:  Failed Hard Drives and RAID

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Definition Contributed By Wes Peterson:

Wes Peterson is a Senior Programmer Analyst with Prestwood IT Solutions where he develops custom Windows software and custom websites using .Net and Delphi. When Wes is not coding for clients, he participates in this online community. Prior to his 10-year love-affair with Delphi, he worked with several other tools and databases. Currently he specializes in VS.Net using C# and VB.Net. To Wes, the .NET revolution is as exciting as the birth of Delphi.

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