But you assume a managed PDU. Why get those when cheap "power sticks" provide outlets. That way you have no way of knowing how heavy a load there is unless you actually read specs (HA! who has time with no working backups!) or use an external power meter. The poor man's way is to physically touch the breaker for the rack strip under full load. If it's warm, probably OK. If it's hot, probably not. If it sizzles the finger tip oil, the breaker is bad and you are soon to need fire protection (Seen this! fun day!).<br>
<br>But, yes, a total load greater than the available single PDU supply is not acceptable. Had to teach that to a newbie today. blade center plus 4 power PC systems = 30A at 220V. But a L6-30 socket is load rated for 24A, not 30. So need to drop 6A off the duals. He protested with "But it's split across the two PDUs". Um. until one goes down, maybe. Which PS is primary is indeterminate when both have power. Some rigs split the load and some don't.<br>
<br><div class="gmail_quote">On Thu, Oct 11, 2012 at 5:51 PM, Brian Mathis <span dir="ltr"><<a href="mailto:brian.mathis+ale@betteradmin.com" target="_blank">brian.mathis+ale@betteradmin.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
That actually is what dual power supplies are for, and it's not a<br>
problem as long as you configure load shedding on the PDU. In a<br>
situation like this, you only lose the low priority stuff. Otherwise<br>
there's little point to having redundant power feeds.<br>
<span class="HOEnZb"><font color="#888888"><br>
<br>
❧ Brian Mathis<br>
</font></span><div class="im HOEnZb"><br>
<br>
On Thu, Oct 11, 2012 at 3:54 PM, Jeff Hubbs <<a href="mailto:jhubbslist@att.net">jhubbslist@att.net</a>> wrote:<br>
</div><div class="HOEnZb"><div class="h5">> Yeah, actually: deciding that dual power supplies on servers were "for<br>
> redundancy" - but not the right kind, and wiring each one up to separate<br>
> circuits. Do that all or most of the way up a rack until PDUs on both<br>
> sides are nearly maxxed out, such that when one power supply fails, that<br>
> server's entire load falls on the other PDU and trips its breaker - then<br>
> the first PDU's break trips in milliseconds because the entire load just<br>
> got dumped on it...crash the whole rack. Of course, the bosses wouldn't<br>
> listen to the EE major who saw this coming, and the guys who cabled up<br>
> this house of horrors are probably still there...<br>
><br>
> Wonder why I left the industry??<br>
><br>
><br>
> On 10/11/12 3:30 PM, Boris Borisov wrote:<br>
>> <a href="http://tuts.pinehead.tv/2012/10/10/how-to-make-your-boss-angry-bad-linux-sysadmin-practices/" target="_blank">http://tuts.pinehead.tv/2012/10/10/how-to-make-your-boss-angry-bad-linux-sysadmin-practices/</a><br>
>><br>
>> Can you add something to it ?<br>
<br>
_______________________________________________<br>
Ale mailing list<br>
<a href="mailto:Ale@ale.org">Ale@ale.org</a><br>
<a href="http://mail.ale.org/mailman/listinfo/ale" target="_blank">http://mail.ale.org/mailman/listinfo/ale</a><br>
See JOBS, ANNOUNCE and SCHOOLS lists at<br>
<a href="http://mail.ale.org/mailman/listinfo" target="_blank">http://mail.ale.org/mailman/listinfo</a><br>
</div></div></blockquote></div><br><br clear="all"><br>-- <br>-- <br>James P. Kinney III<br><i><i><i><i><br></i></i></i></i>Every time you stop a school, you will have to build a jail. What you
gain at one end you lose at the other. It's like feeding a dog on his
own tail. It won't fatten the dog.<br>
- Speech 11/23/1900 Mark Twain<br><i><i><i><i><br><a href="http://electjimkinney.org" target="_blank">http://electjimkinney.org</a><br><a href="http://heretothereideas.blogspot.com/" target="_blank">http://heretothereideas.blogspot.com/</a><br>
</i></i></i></i><br>