We optimize the server BP. Two for 800W or two for 450W + PowerSafeguard?

How to calculate which PSUs are sufficient to ensure the continuous operation of the server? The answer is not as straightforward as it would seem. To calculate the maximum power consumption of all components and ensure the delivery of the required power from one PSU, and then install two such power supplies in the server for redundancy - this is the traditional approach. However, thanks to PowerSafeguard technology, in most cases, you can get by with power supplies with a lower nominal value than is required by the results of this calculation, and at the same time be sure of the server’s performance.

PowerSafeguard is a technology that provides automatic control of server power consumption to maintain continuous operation in case of failure of some power supplies, if the remaining PSUs power is not enough for a full load. Fujitsu has been offering this technology for some time in its servers RX200 S7, RX300 S7, RX350 S7, TX300 S7. All these servers use standardized PSUs of two types - 450 W or 800 W.

PowerSafeguard allows you to operate the server on 450 W power sources and ensure continuity of operation when one of the PSUs fails, even if the peak power consumption of this configuration can theoretically exceed 450 W (the permissible excess of the peak load over the PSU rating is 30%, i.e. configurations with a theoretical peak power consumption of up to 585 watts will be able to work on a 450 W PSU).

In situations where the real power consumption of the system is on the verge of power supply capabilities, PowerSafeguard technology reduces the p-state (respectively, the clock frequencies of the processor cores), ensuring the total power consumption of the system within the power of one power supply. Server continuity is guaranteed, although in someperiods of time system performance will be reduced.

Explain the essence of technology is convenient by example. Take the PRIMERGY RX300 S7 server. Let it have a fairly rich configuration - two Xeon E5-2680 processors, 24x4 = 96GB of memory, 8 SAS disks, PCIe-SSD on 1.2TB, RAID 5/6 with FBU, a FibreChannel controller and a BlueRay writer.

The peak power consumption of this system can be checked by the PowerCalculator function in the Fujitsu configurator . We look at the load on the PSU, that is, DC-load.

At maximum server load, it will be 524.8 watts. Of the two possible options for power supplies (450 W and 800 W), there is a desire to put the second. However, we will supply 2x450 watts. Naturally, two of these PSUs fully pull the load, while working in a balanced mode. What will happen if one of them burns out?

It should be noted that the power consumption of the server is not constant, but varies depending on the server load (thanks to the flexibility of the Intel Xeon E5 platform, including TurboBoost 2.0 technology). The graph of power consumption over time will look like a wavy line.

As the same PowerCalculator shows, with a very typical server load level of 70% - it consumes no more than 378 watts!

That is, in most cases, even a richly configured server will continue to work perfectly on a single 450-watt power supply. However, where we would have peaks of power consumption with two power supplies - PowerSafeguard will work. Through the built-in server management chip (iRMC), p-state processors will be reduced to the minimum, and then it will increase until the power consumption "rests" in the limit of the power supply, or until it turns out that it is not necessary to limit the processor - since reducing server load this limit will be met without the intervention of PowerSafeguard technology.

Thus, when working in “emergency” mode (on one power supply, until the second is restored to working capacity), a decrease in productivity will be observed only for certain periods of time. At the same time, in the case of a typical download server about 70%, full performance will be available. Only “bursts” of the chart are cut off.

Naturally, for a specific configuration, it is better to check the energy parameters for different downloads using a calculator. But I would like to note that for the example we took a really “predatory” configuration for energy consumption, and most of the most popular server configurations of this type even in peak situations consume less than 450 watts. So the use of 450-watt PSUs instead of 800-watt is justified. In addition to the price, I’ll add an argument: power supplies have the greatest energy efficiency at a high degree of load, therefore, from the point of view of energy efficiency, a 450 W power supply that works with a load of more than 60% is better than an output of the same power supply of 800 W, loaded by 34%.

Also popular now: