IEEE Spectrum's Tech Titans Building Boom is a wide-ranging looking into the mega data center phenomenon - the surge in the construction of facilities holding tens of thousands, even 100K+, servers. The article has a wealth of interesting details, some of which are noted below, but doesn't address the larger sustainability issues - business or environmental. Will this herald a a new generation of online and cloud services? Or will it, like the fiber optic surge of the 1990s, result in capacity that overshoots demand and causes a recession within the provider community?

And while data center operators are claiming exceptional power usage effectiveness (PUE) ratios, we're still talking about facilities that consume 20-200 MW apiece and emit a considerable carbon footprint unless powered by renewable energy.

Some of the technologies that are drive these mega data centers:
- modular containers that can hold 1000+ servers, along with their power and cooling
- replacement of tradition chiller cooling with lower-energy technologies like water-based evaporative cooling or air-side cooling
- new power schemes ranging from demand-based dynamic voltage/frequency scaling to high-voltage DC power distribution to proprietary UPS technology.

It is unclear how or when these technologies will migrate beyond the mega data center niche. I have long felt that air-side cooling - use of the cooler air which surrounds most of the world's data centers most hours - is an underutilized option.

Update: 2009.06.29
Microsoft announced that its Dublin, Ireland and Chicago, USA data centers will come online in July. Current/potential critical power ratings are 5.4/22 MW and 30/60 MW, respectively. Microsoft is aiming for an impressive "PUE yearly average calculated at 1.22".

Update: 2009.09.25
More on the Google/Belgium and Microsoft/Dublin mega data centers, which are both now online.

Update: 2009.09.28
Mega data centers can become the focus of tax and regulatory controversies.

Update: 2010.01.26
Infoworld reports that Facebook broke ground today on facility in Prineville, OR, that is targeted to achieve a PUE of 1.15.
More immediate than future targets are Google's quarterly online reports of "the PUE results from all Google-designed data centers with an IT load of at least 5MW and time-in-operation of at least 6 months. The trailing twelve-month (TTM), energy-weighted average PUE for all of these facilities is 1.19...with at least one facility returning a TTM PUE of 1.13. Our lowest published quarterly average PUE of an individual facility is 1.11." Would that all data center operators be this transparent.