Server are normally delivered with single or redundant Power Supply Unit (PSU). Redundant PSU means that you've got two physical power supply units, both with enough capacity to power the whole server alone.

Servers can be delivered with redundant PSU and only one power cord, a setup that WebDeal does not recommend. We only use redundant PSU with two or more power cords in order to be able to handle cable or power circuit failure without interruption on the server.

What can normally interrupt power supply ?

The overall goal with all types of redundancy, including PSU redundancy, is to increase uptime and system stability. A number of different problems can interrupt a server's power supply, such as:

• PSU hardware failure
• PSU hardware failure due to high voltage
• PSU hardware failure due to short circuit
• Power cord unplugged
• Power cord failure
• Power circuit failure

All these problems will cause interruption on the server if a single PSU server is used. With a redundant PSU server that is correctly wired, on the other hand, such failures will not affect the server's uptime.

Correct wiring of a redundant PSU server

A common mistake while wiring a redundant PSU server is to connect both PSUs to the same power circuit. In addition to causing downtime at the event of a power circuit failure, this can also result in both the PSUs failing due to high voltage or short circuit.

WebDeal will always carefully wire our servers with a “share nothing” design. Each server with redundant PSU will be connected to:

• 2 separate power administration units
• 2 separate power breakers
• 2 separate battery backups
• 2 separate backup power generators

All this is done to maximize the value that redundant power supply design can give to a server.