[Sysadmins] Dell PowerEdge R210

Nick Hilliard nick at netability.ie
Mon Sep 9 13:10:29 IST 2013

On 08/09/2013 12:26, Harry Duncan wrote:
> The concept works better for servers with larger power supplies than this,
> or in the scenario where you have a cluster of servers. If they are
> deployed in an office where there is a typical 10 hour usage, suspending to
> ram for the dark hours could save quite a chunk of change on energy costs.

ok, i had been thinking more of data centre deployments and stuff, rather
than office installation.

> A single 500W psu suspended for every weekend of a year should yield 225
> euro in electric costs savings

well not really because 500W is the nominal maximum rating of the psu, not
the actual power draw of the server.  E.g. a standard 1U server with q-core
cpu and a bunch of disks might have dual 500W PSUs, but the actual power
draw will probably be around 120-180W, depending on various factors (e.g.
whether the CPU is busy or not).  So the savings are much less than you're
suggesting here.

A couple of years ago, Lidl had a great plug-in power meter which was
surprisingly accurate given its cost (about €10 at the time, and it also
handled pF).  I haven't seen them on sale recently, but if you get the
opportunity to get something like it, it's worth using in anger to see how
much things actually cost.  The results can be surprising.  I have retired
quite a lot of kit based on the output of power readings, i.e. purely on an
opex basis.

> Ireland is one of the few places where we don't take the energy shortage
> crisis seriously, credit to the ESB I guess.

we have one of the highest retail power costs in europe which should give
people some inclination to reducing their power requirements.  The problem
is more related to ignorance and lack of information about how to do
accurate power / cost analysis.


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