[ale] is advanced power management a good idea on a server?

[Jeff Hubbs]

Chris -

My feeling is that it's a bad thing to let server innards endure a lot
of temperature slews.  APM is going to do that.  Your drives really
ought to run all the time, too.

On the other hand, I can see taking advantage of APM to deal more
effectively with power and cooling outages.  In other words, when the
computer hooked to your data center UPS detects that the UPS has gone on
battery, have it fire off a message to the server to engage APM (if
there's a way to do that on the fly).  

If there isn't a good way to enable APM modes remotely on a server
without taking it down, OK - enable APM and just have it run SETI at home
or something all the time, having it execute a killall setiathome when
the power goes out.

Many times, in a data center setting, you can go a long way toward not
needing a generator by setting up a way to automatically step down the
load on the UPS during a power outage.

I had just such a scheme all planned out at a previous employer.  I had
just put in a new big hockin' UPS and I was trying to keep the company
from having to buy a generator - I was able to show via cost-benefit
analysis that a generator wouldn't pay for itself until the power was
out for far longer than any outage the building had ever experienced
(according to Georgia Power data).  After they laid me off along with a
few other people, one of the first things they did was...buy a
generator.  One of the ironic things was that if I had known there were
going to be a generator, I would not have spent more money to fit the
UPS with the maximum number of batteries.  My objective was to try to
use a computer attached to the UPS (running Linux, of course) to
automatically coordinate a shutdown of the equipment in the data center,
so as to preserve connectivity to and operation of the primary
AlphaServer cluster nodes for as long as possible.  

Another irony:  Part of my plan was to replace the 9-10 CRT screens in
the data center with just two flat-panel monitors, a two-head KVM
switch, and a Linux box with a multiport serial adapter in it - the
reason being to reduce the power and cooling load and let the UPS run
longer when it was engaged.  My request was rejected because flat-screen
monitors were viewed as highly indulgent luxuries.  

If anyone knows of anyplace that would be interested in having me work
on building an setup like that, let me know right away - I'm still
itching to do it and I need income!

- Jeff


Chris Bergeron wrote:
> 
> Is it ever a good idea to have APM on a server?
> 
> I have a feeling not, but I'm wondering if there are any other opinions
> out there...
> 
> CB
> 
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