Redundant Array of Independent Disks is a method of storing data on multiple disks and in such a way that the performance can be improved.
The I/O operations can be balanced in such a way so as to increase the overall performance of the data storage and retrieval.
To the operating system the RAID disks appears as a single logical hard disk.
A technique called striping is employed by RAID and involves partitioning the drive's storage space into multiple units ranging from a sector (512 bytes) up to several megabytes.
The stripes of all the disks are interleaved and addressed in order. There are different types of RAID depending on the performance and the budget of the system.