Quick survey -- UPSs on slave nodes?

Ray Muno muno at aem.umn.edu
Mon Feb 10 13:59:57 PST 2003

In our situation, we have all of our cluster nodes on UPS protected circuits.

I would not view our power as being reliable enough to want to trust the 
large investment the cluster represents to the fluctuations we see on the
power lines.  If our power disappears for more than a few minutes, we 
can start shutting things down and shedding load, extending our runtime
for the critical parts like disk servers and such.

I would clarify, however, that I would invest in one large UPS than have 
a bunch of small ones.  In this scenario, we have one source of power 
that we are not directly sharing with all the laser printers and copiers
in the building.  Much has been said in this newsgroup regarding undersized
neutrals and inadequate wiring.   Any UPS system should have the ability 
of removing it from the line and transferring the load to line power for
service.  UPS's rely on batteries and they definitely require service 
over the years.  I have small UPS's in some remote wiring closets that
have caused me more grief then they were worth.  When the power would drop,
they would run for a minute and go dead, never to return.   Before the failure,
they would report as being online with an hour of runtime.  They ended up
needing batteries.  In order to service them I have to unplug everything
from the UPS and move it over to line power. 

When we installed our clusters, we just viewed the UPS as part of the facility
cost along with air conditioning.  Many of people tend to overlook the 
facility costs involved in running a cluster but they are significant,
especially when the clusters get large.  

On Mon, Feb 10, 2003 at 11:24:07AM -0800, Nicholas Webb wrote:
> At the University of Idaho we are preparing to order a new beowulf cluster
> and a vendor seemed to be shocked that we wanted UPSs attached to ALL of
> the nodes.  He stated that most people only use UPSs on the Master Node,
> unless the cluster was used for some kind of mission critical purpose.
> So the question, do you use UPSs on your slave nodes?  Arguments for not
> using UPSs on slave nodes (and vice versa)?
> Thanks!
> --
> Nick Webb
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 Ray Muno                           http://www.aem.umn.edu/people/staff/muno
 University of Minnesota                          e-mail:   muno at aem.umn.edu
 Aerospace Engineering and Mechanics               Phone:     (612) 625-9531
 110 Union St. S.E.		                     FAX:     (612) 626-1558
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