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Simple question - ilO power settings take effect immediately?

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Simple question - ilO power settings take effect immediately?

A question from Kelly:




Sorry for asking another basic question – but have not found it yet in a document and need to confirm for a customer….


If a customer changes the iLO Power Management setting via iLO, it appears no reboot is required for it to be activated (immediately happens) – is that correct?   I have always assumed it was immediate, but wanted to be 100% sure before I confirm answer the customer.


   ( assuming the same will be for ilO 2, 3 and 4)










Multiple replies:


From David:

In general, BIOS settings that affect the host are read in during boot while the processor in is real mode; once the processor has transitioned to protected mode to run an x32/x65 OS, it no longer can access the BIOS space, so it has to grab them beforehand.  That is why so many settings require a reboot to make the host aware of them because it can’t ask after the OS is loaded.

Everything you’re talking about below is in the iLO’s domain, so reboot not required…


Input from Stefan:

I seem to remember that to/from OS Control mode requires a reboot, the rest is on the fly.


Reply from David:

Correct. As stated in “ HP ProLiant server power management on SUSE Linux Enterprise Server 11 SP2 “ whitepaper:

The Power Regulator Settings can be adjusted through the ROM-Based Setup Utility (RBSU) or HP iLO 4 interface as shown in Figure 1. Transitions to and from OS Control require a system reboot for the change to take affect but the system can be changed between the other three modes dynamically.”.


Also, be aware that from iLO you will change only the Power Regulator settings.

If the intent is to change the Power Profile (which include changes on Power Regulator, C-States, Memory interleaving,..), then you’ll need to go into RBSU or use scripting tools to change Bios settings.




Any other comments or suggestions?