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Power to the People

By Jessie Frazelle

Communications of the ACM, Vol. 63 No. 8, Pages 41-45

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When you upload photos to Instagram, back up your phone to the cloud, send email through Gmail, or save a document in a storage application like Dropbox or Google Drive, your data is being saved in a datacenter. These datacenters are airplane-hangar-sized warehouses, packed to the brim with racks of servers and cooling mechanisms. Depending on the application you are using, you are likely hitting one of the datacenters operated by Facebook, Google, Amazon, or Microsoft. Aside from those major players, which I refer to as hyperscalers, many other companies run their own datacenters or rent space from a colocation center to house their server racks.

Carbon footprints. Most of the hyperscalers have made massive strides toward achieving carbon-neutral footprints for their datacenters. Google, Amazon, and Microsoft have pledged to decarbonize completely; however, none has yet succeeded in that quest.


Alessandro Ratti

The base of the discussion in the article is "PUE" must be nearest to 1.0 as possible to have a better data-center.
PUE is basically a design parameter for the infrastructure of the data center, for sure lower is better, and 1.0 is the lower bound.
In theory, as soon as you design the data-center infrastructure with a specific PUE, any type of server boards, which fits into the data-center power envelope, will work; this board update possibly changes the final data-center computational capabilities, with the whole data-center still wasting the same amount of power.
But the article starts with discussion about how the data-center are becoming green, or, maybe better, how data-center owners want to say they are becoming green.
Using PUE to define how green is a data-centre is misleading: the denominator for the PUE value is "the energy used for servers" ( re-read energy going to the server CPU boards ), but the data center output is not "energy" but useful computation for the customer.
A Green-er data center must provide high output for same energy input: in the HPC a GREEN500 computer must have the highest value of GFlops/Watt ( the maximum now is about 21 ); a Green data-center must provide an highest customer useful computation for the give input power, and these number can be used for an effective "green" comparison ( SERT good starting point ? www.spec.org )
This value can be changed by changing the server boards, as already discussed above.
New technology advances enable good gain in computational efficiency, but many energy items in the final equation will not scale in the same way: for example, more powerful server boards typically need also faster or more topologically complex communication infrastructure.
To be green a data-center must be also well balanced is energy use when changing load conditions: less workload, the capability to shut off unused servers to save power; but this feature will also not scale ( a fully unused data-center is pure waste ).
Data center will use about 1% of the world energy ( https://science.sciencemag.org/content/367/6481/984 ) and any save is welcomed.

I want to add another input on the "FAANG" being carbon neutral now or later in the future : does, in the carbon balance, they include the carbon produced by building the data-center ? I do not know, but many times the calculation for being "carbon neutral" is related only to the operation of the facility ( energy in-out during facility lifetime ) with no consideration for the carbon cost of building and de-commissioning.
And, in general, how is the whole data-center business "green" ? how is the impact of building a new undersea cable ( see Marea https://news.microsoft.com/marea/ ) which is needed to support the data-center business ?

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