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This post discusses the Standard IBM Bladecenter Chassis, not the T -or H Chassis systems.

 

A common warning message you might recieve from an IBM Bladecenter is as follows:

"Demand exceeds a single power module. Throttling can occur in power domain 1."

The message is normal.

In a normal rudundant situation, all power needs are drawn from both PSU's, so you effectively have 2 x 2000 = 4000w for a single power domain during normal running. Its not a fail-over system, its drawns its power from both PSU's at the same time. So its kinda like 'load balencing'.


In a NON-redudant situation, so when you loose a single power domain, the bladecenter will only have 2000w left per power domain.

For 8 servers, its drawing more than 2000, as you saw, 2418 or therabouts.

With the power policy "Redundant with potential performance impact", the bladecenter will attempt to clock-down some of the blades servers until the powerconsumption is below 2000w, so it can keep running.

The clocked down servers will of course suffer the "performance impact".

In short: The Bladecenter you are using is not able to support all blades at full performance, IF you loose power redundancy.
Therefor, actually, these bladecenters can not be considdered "fully redundant" .
It may not suprise you that IBM, not its partners, do not like to easily admit to this limitation.

In the meantime, the warning remains, to remind you that this may happen when you loose redundancy.

There are 2 workarounds:
1. Redistribute your blade servers across both power domains evenly, so you dont use more than 2000 watt per power domain. If you place more servers this will be come unattainable though.

2. Make sure all 4 PSU's are connected to a redundant power source, so backup power (with generator). This more or less circumvents the entire problem.


Posted on Thursday, June 1, 2006 1:48 PM Tech , IBM | Back to top


Comments on this post: IBM Bladecenter power warning

# re: IBM Bladecenter power warning
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When I talked with IBM about this they indicated that the problem is actually a reporting issue and not a "real" problem. They supplied me with the update to correct this problem, which I was able to do to one entire blade center. This will change the reporting to 230W in the fuel gauge instead of 260W+ Unfortunately, now that I have five blade centers, and 4 of these report the 260W+ I cannot locate the fix. However, I do have one blade that reports correctly, but the differences are in the wrong direction. The diagnostics is 1.02, where the others are 1.03 or better. This is a little discouraging. Not to mention the blades that have all of the correct values have varying levels of firmware. This is a result of 4 blades being replaced by IBM.

I will continue to search my emails and if I find the fix I will be happy to share. It is always nice to see the status as green instead of the exclamation mark.

Damien Lujan
Left by Damien Lujan on Sep 06, 2006 2:41 AM

# re: IBM Bladecenter power warning
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The BladeCenter's power supplies & fans are on unless you unplug the power cords. Is it good that there is no other way to turn off the power, e.g. power on/off button on the chassis?
Left by Scott on Dec 28, 2006 12:56 AM

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