[Beowulf] Re: Building new cluster - estimate (Ivan Oleynik)

Mark Hahn hahn at mcmaster.ca
Fri Aug 1 09:12:00 PDT 2008

>> the thing I don't like about controlled PDUs is that they're pretty
>> harsh - don't you expect a higher failure rate of node PSUs if you go 
>> yanking the power this way?
> Why?
> If nodes shutdown, on commands from the scheduler, that is good.
> And, if they do not, how is cutting power by the PDU socket any different 
> than a power switch on the node?

I don't design PSU's, but yanking the cord seems "rude" compared to 
simply raising the "please power off" signal.  the latter is part of 
all PSU's these days, and is what IPMI uses (via I2C, I guess).
perhaps it's superstition - I do always prefer to use the off button,
rather than ranking the cord.  but thinking of how a switching PSU works,
perhaps it doesn't really matter - it views the input power as highly
variable anyway (ie, 90-250V, and with that annoying 50-60 Hz flutter ;)

>>> If you set your machines BIOS to start on power up, it is trivial to stop 
>>> and start machines with the PD U power, and that is definitely reliable.
>> huh?  we're talking about network-attached IPMI, which is fully independent
>> of the controlled motherboard's bios.  are you talking about those hybrid 
>> systems where the IPMI controller shares an ethernet port with the host?
>> or IPMI through a kernel driver?
> Either.
> Most share a port, some have dedicated ports on board.

I'm not sure about the "most" part - HP's don't, and it looks like supermicro
offers options both ways.  all the recent tyan boards I've looked at had 
dedicated IPMI/OPMA onboard.  all HP machines have dedicated ports.

but to me this has all the hallmarks of a religious issue, so...

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