This configuration is taken from the packaging of a Promise controller. The data storage illustration is easy to follow, which in this example is on a total of four hard drives.

A RAID 5 requires at least three hard drives and operates all drives almost simultaneously. In order to ensure data security, a parity bit is calculated for each information unit and saved on one of the available drives on a rotating basis.

Now the question arises: what is the ideal number of drives? More drives fundamentally mean a greater risk of failures as well as higher energy requirements, while performance may suffer to an unacceptable degree with only a few drives. We tested all configurations, using up to eight drives.