Araid structure is primarily used for security reasons is primarily used to ensure higher data reliability stands for redundant arrays of inexpensive disks is primarily used to decrease the dependence on disk drives

b) A RAID structure is primarily used to ensure higher data reliability,

Explanation:

A set of hard disks configured as a RAID (Redundant Array of Independent Disks) , even is composed by several separate disk units, in their different configurations (RAID 0, 1, 2 or 5 being the more usual) behave like it were a single logical unit.

The information to be stored is divided in blocks (at a byte or bit level) and stored in several disks instead of a single one.

Depending on the type of RAID used , the information (except for RAID 0) is mirrored or encoded in a redundant fashion, so if eventually a disk drive fails, the remaining disks can be used in order to reconstruct the lost information.

So, the main purpose of  a RAID array is to be able to retrieve the stored data in the event of a disk failure, which ensures higher data reliability.  

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