For power budgets under 675W, installing a second power supply provides redundancy. To install a second power supply, use the IBM High Efficiency 675W Power Supply, part number 60Y0332. Installing four power supplies ensures redundancy even with a fully loaded server. To install the third and fourth power supplies, use this IBM 675W Redundant Power Supply Kit, part number 60Y0327. The power subsystem is designed for N+N operation and hot-swap exchange. Having four power supplies installed allows for N+N redundancy, where N=2 (that is, a total of four power supplies where two are redundant backups for the other two).