What is the Raid concept?

Answer 1

RAID or Redundant Array of Inexpensive Disks, is a method and technology of using multiple disks for increased size, performance, or redundancy.

Imagine a tree, with each branch a different combination of mirroring, concatenation, striping, and parity. Combine this with hot spares, a high reliability can be achieved.

The mirroring of drives makes them clones of each other, a physical redundancy in the case one dies.

The concatenation of drives makes them appear as one large drive. This reduces redundancy as data is split between drives.

The striping of data across drives, improves performance by dividing work. While one drive is writing, another drive can accept the next data to write. This reduces redundancy as data is split between drives.

Parity is a calculated value, used to reconstruct data when a drive fails. Parity can be striped, or be assigned to a dedicated drive for parity only.

Hot spares are automatically activated, and data is remirrored from the other or reconstructed from parity.