What is RAID?
Depending on who you ask, RAID either
stands for Redundant Array of Inexpensive
Disks, or Redundant Array of Independent
to the former school of thought, point
out (and quite rightly too) that the word
"Inexpensive" was used by the
scientists at the University of California
at Berkeley who first conceived of RAID.
Detractors however, note that hard drives
are anything but "Inexpensive,"
and that "Independent," would
have been a more apt term.
Whatever the acrimony over acronyms, the original meaning of RAID
seems much more appropriate today than it did in 1987 when Patterson,
Gibson, and Katz published a paper entitled, "A Case for Redundant
Arrays of Inexpensive Disks." Hard drives after all, are
cheaper than ever before, offering gargantuan storage capacities
at relatively low prices.
Research on RAID
Researchers came up with the idea of
RAID while looking for ways to improve
hard drive storage reliability and performance.
The concept initially consisted of clustering
small, "inexpensive" disk drives
together into an array so that the array
would appear to the system as a single
During initial testing, it was discovered that an array of drives
could actually deliver performance exceeding that of single, more
expensive hard drives.
There was just one problem however -- a problem which underscores
the importance of RAID data recovery. The Mean Time Before Failure (the
average time before a failure will occur) in a RAID, was reduced
due to the probability of any one drive in the array failing. Consequently,
researchers proposed five levels of RAID
to provide a balance between performance and data protection.
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