How does the system load the Power supplies under the "Dynamic Power Saver" mode

[chuckk281]

Joe had a power management question:

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Customer asked:

How does the system load the Power supplies under the "Dynamic Power Saver" mode.

Which are on and which are in standby?

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From Ken:

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The lower numbered power supplies on each side of the enclosure are used first.  In a typical enclosure you will see power supplies 1,2,4 & 5 being used.  In a lightly loaded enclosure, only power supplies 1&4 will be used.

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Hope this helps. Have you had good success using "Power Saver" mode?

[chuckk281]

Arnout had some additional good info:

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See the paper on http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00816246/c00816246.pdf  p.28

Most power supplies operate more efficiently when heavily loaded and less efficiently when lightly

loaded. Dynamic Power Saver mode provides power load shifting for maximum efficiency and

reliability. Dynamic Power Saver technology maximizes power supply efficiency to reduce operating

costs. Power supply efficiency is simply a measure of DC watts output divided by AC or DC watts

input. At 50% efficiency, 2000W input would yield 1000W output. The difference is costly wasted

energy that generates unnecessary heat.  

Dynamic Power Saver mode is active by default since it saves power in the majority of situations.

When enabled, Dynamic Power Saver runs the required power supplies at a higher use rate and puts

unneeded power supplies in standby mode. A typical power supply running at 20% load could have

an efficiency rating as low as 60%. However, at 50% load, the efficiency rating could be up to 94%,

providing a significant savings in power consumption.

In the first example in Figure 21, without Dynamic Power Saver, power demand is low and spread

inefficiently across six power supplies. In the second example, with Dynamic Power Saver active, the

power load is shifted to two power supplies for more efficient operation. The remaining power

supplies are placed in a standby condition. When power demand increases, the standby power

supplies instantaneously deliver the required extra power. This enables the power supplies to operate

at optimum efficiency, with no effect on redundancy.

Dynamic Power Saver is enabled by the BladeSystem Onboard Administrator module. When

enabled, this feature monitors the total power consumed by the enclosure in real-time and

automatically adjusts for changes in demand. 

In redundant environments, at least two power supplies are

always active, and the maximum load that can be reached on

any power supply is 50%. Once the 50% load is reached,

another two power supplies are activated to ensure that

redundancy is maintained at all times.

As to which PSU’s are powered on first, see the attached xls.