[ale] Little OT: Bad Linux Sysadmin Practices

[Jim Kinney]

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!).

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.

On Thu, Oct 11, 2012 at 5:51 PM, Brian Mathis <
brian.mathis+ale at betteradmin.com> wrote:

> That actually is what dual power supplies are for, and it's not a
> problem as long as you configure load shedding on the PDU.  In a
> situation like this, you only lose the low priority stuff.  Otherwise
> there's little point to having redundant power feeds.
>
>
> ❧ Brian Mathis
>
>
> On Thu, Oct 11, 2012 at 3:54 PM, Jeff Hubbs <jhubbslist at att.net> wrote:
> > Yeah, actually:  deciding that dual power supplies on servers were "for
> > redundancy" - but not the right kind, and wiring each one up to separate
> > circuits.  Do that all or most of the way up a rack until PDUs on both
> > sides are nearly maxxed out, such that when one power supply fails, that
> > server's entire load falls on the other PDU and trips its breaker - then
> > the first PDU's break trips in milliseconds because the entire load just
> > got dumped on it...crash the whole rack.  Of course, the bosses wouldn't
> > listen to the EE major who saw this coming, and the guys who cabled up
> > this house of horrors are probably still there...
> >
> > Wonder why I left the industry??
> >
> >
> > On 10/11/12 3:30 PM, Boris Borisov wrote:
> >>
> http://tuts.pinehead.tv/2012/10/10/how-to-make-your-boss-angry-bad-linux-sysadmin-practices/
> >>
> >> Can you add something to it ?
>
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-- 
-- 
James P. Kinney III
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