Power supplies come in 2N and N+x redundant configurations

XTRONICS Emerson Industrial Automation SDN Series power supplies are available in 2N and N+x redundant configurations. Units include built-in current sharing for parallel and redundant operation and can be used in applications that require true redundant operation. All models ending in P also include a DC OK status relay contact. The external SDN 2.5-20RED and SDN 30/40RED modules increase reliability by isolating the supplies and adding more signal options. Paralleling for increased power does not require the use of these modules.

http://www.xtronics.ca