Wikipedia
RAID ( "Redundant Array of Inexpensive Disks" or "Redundant Array of Independent Disks") is a data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both This was in contrast to the previous concept of highly reliable mainframe disk drives referred to as "single large expensive disk" (SLED)Data is distributed across the drives in one of several ways, referred to as RAID levels, depending on the required level of redundancy and performance The different schemes, or data distribution layouts, are named by the word "RAID" followed by a number, for example RAID 0 or RAID 1
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