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Re: rack power question

  • From: Marshall Eubanks
  • Date: Mon Mar 24 01:14:21 2008

The interesting thing is how in a way we seem to have come full circle. I am sure lots of people can remember large rooms
full of racks of vacuum tube equipment, which required serious power and cooling.
On one NASA project I worked on, when the vacuum tube stuff was replaced by solid state in the late 1980's,
there was lots of empty floor space and we marveled at how much power we were saving. In fact, after
the switch there was almost 2 orders of magnitude too much cooling for the new equipment (200 tons to 5 IIRC),
and we had to spend good money to replace the old cooling system with a smaller one. Now, we seem to have expanded
to more than fill the previous tube-based power and space requirements, and I suspect some people wish they could get
their old cooling plants back.


On Mar 23, 2008, at 5:23 PM, Joel Jaeggli wrote

Ben Butler wrote:
There comes a point where you cant physically transfer the energy using air
any more - not less you wana break the laws a physics captin (couldn't
resist sorry) - to your DX system, gas, then water, then in rack (expensive)
cooling, water and CO2. Sooner or later we will sink the hole room in oil,
much like they use to do with Cray's.

The problem there is actually the thermal gradient involved. the fact of the matter is you're using ~15c air to keep equipment cooled to ~30c. Your car is probably in the low 20% range as far as thermal efficiency goes, is generating order of 200kw and has an engine compartment enclosing a volume of roughly half a rack... All that waste heat is removed by air, the difference being that it runs a around 250c with some hot spots approaching 900c.

Increase the width of the thermal gradient and you can pull much more heat out of the rack without moving more air.

15 years ago I would have told you that gallium arsenide would be a lot more common in general purpose semiconductors for precisely this reason. but silicon has proved superior along a number of other dimensions.

Alternatively we might need to fit the engineers with crampons, climbing
ropes and ice axes to stop them being blown over by the 70 mph winds in your
datacenter as we try to shift the volumes of area necessary to transfer the
energy back to the HVAC for heat pump exchange to remote chillers on the
In my humble experience, the problems are 1> Heat, 2> Backup UPS, 3> Backup
Generators, 4> LV/HV Supply to building.
While you will be very constrained by 4 in terms of upgrades unless spending
a lot of money to upgrade - the practicalities of 1,2&3 mean that you will
have spent a significant amount of money getting to the point where you need
to worry about 4.
Given you are not worried about 1, I wonder about the scale of the
application or your comprehension of the problem.
The bigger trick is planning for upgrades of a live site where you need to
increase Air con, UPS and Generators.
Economically, that 10,000KW of electricity has to be paid for in addition to
any charge for the rack space. Plus margined, credit risked and cash
flowed. The relative charge for the electricity consumption - which has
less about our ability to deliver and cool it in a single rack versus the
cost of having four racks in a 2,500KW datacenter and paying for the same
amount of electric. Is the racking charge really the significant expense
any more.
For the sake of argument, 4 racks at £2500 pa in a 2500KW datacenter or 1
rack at £10,000 pa in a 10000KW datacenter - which would you rather have?
Is the cost of delivering (and cooling) 10000KW to a rack more or less than
400% of the cost of delivering 2500KW per rack. I submit that it is more
that 400%. What about the hardware - per mip / cpu horse power am I paying
more or less in a conventional 1U pizza box format or a high density blade
format - I submit the blades cost more in Capex and there is no opex saving.
What is the point having a high density server solution if I can only half
fill the rack.
I think the problem is people (customers) on the whole don't understand the
problem and they can grasp the concept of paying for physical space, but
cant wrap their heads around the more abstract concept of electricity
consumed by what you put in the space and paying for that to come up with a
TCO for comparisons. So they simply see the entire hosting bill and
conslude they have to stuff as many processors as possible into the rack
space and if that is a problem is is one for the colo facility to deliver at
the same price.
I do find myself increasingly feeling that the current market direction is
simply stupid and had far to much input from sales and marketing people.
Let alone the question of is the customers business efficient in terms of
the amount of CPU compute power required for their business to generate 1$
of customer sales/revenue.
Just because some colo customers have cr*ppy business models delivering
marginal benefit for very high computer overheads and an inability to pay
for things in a manner that reflects their worth because they are incapable
of extracting the value from them. Do we really have to drag the entire
industry down to the lowest common denominator of f*ckwit.
Surly we should be asking exactly is driving the demand for high density
computing and in which market sectors and is this actually the best
technical solution to solve them problem. I don't care if IBM, HP etc etc
want to keep selling new shiny boxes each year because they are telling us
we need them - do we really? ...?
Kind Regards
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
[email protected]
Sent: 23 March 2008 02:34
To: Patrick Giagnocavo
Cc: [email protected]
Subject: Re: rack power question