The Advantages of Dual Power/Redundant Supply Unit Servers – TechMikeNY



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What Is the Advantage of Having Dual Power Supply Units and Will It Cause My Server to Draw More Power?


The majority of the servers that TechMikeNY sells are dual power supply unit servers, or, in other words, come with two power supplies. For the budget conscious, we do provide some configurations with one power supply and the option to add a second power supply. What is the advantage of having a redundant power supply? Simple: if one of the dual PSUs for a server should fail, the other unit will take over since both units are capable of handling the full wattage needed to run the server. For example, if your server pulls 500W total and there are two 750W power supplies installed, if one PSU fails, the other 750W power supply will provide enough power to keep the server running. Additionally, for servers in large data centers, each PSU can be put on a separate circuit – so should one circuit fail, the redundant PSU on the second circuit will take up the full load.


Under normal loads, with two PSU’s in redundancy mode, the PSU’s will split the load 50/50. As such, the dual power supply server will not pull more power or add to your electricity bill with dual PSU’s installed.  As an added safeguard, HP and Dell servers will show errors during boot if the power required exceeds the output of the power supply. Additionally, most PSU’s are hot-swappable – meaning in the event of a failure of one of the units, you can swap out a replacement unit with no downtime to the server.


Bottom line: a redundant or dual PSU is not required for your server to run, but highly recommended to avoid the system crashing due to an electrical or PSU failure. For mission-critical servers, it is considered an essential set-up for system stability.  


  • Thanks for your question below, Yemi. We suppose it’s possible. We have some of our servers plugged into 2 separate UPS battery backups. In the past, we had one battery backup where one PSU was connected to a battery backup and the other PSU was connected to a PDU power strip which was connected directly to AC power. We never had any issue with servers shutting down.
    Did this scenario happen to you? Did the server reboot and give any error messages on power supply issues? HP and Dell servers show errors during boot if the power required exceeds the output of the power supply.

  • Could frequency variation on one part of power source to a server shut it down when such server takes it supply from dual sources?

    Yemi Fajuyi
  • Thanks for your question, Bill. Broadly speaking, the power consumption will be driven by what the server is using. So using a higher-wattage PSU will not necessarily cause the server to use more juice unless it needs it. And if it does need more than 460W to run, you should expect to get errors when booting that the server exceeds the output of the power supply. Of course, all this depends on what you have in the server, e.g., type of CPU, CPU count, type of RAM, amount of RAM, amount of drives, etc. There are some power supply calculators out there, which you can find through Google search. These let you punch in exact parts of your system and tell you estimate of the power consumption. Hope that helps, and thanks for reaching out!

  • Is there difference in power consumption between 460W and 750W power supplies (for the same server configurations)? How to calculate what power supply is most appropriate for my server?


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