Sun’s Software Labs Has a PUE of 1.28

I had blogged before about Sun’s Modular Data Center.

What I missed was their entry on page 15 of the document where  Sun discussed how they consolidate 32 different server labs into one space and achieve a a PUE of 1.28.

Efficiency in Sun’s Santa Clara Software Datacenter
In 2007 Sun completed the largest real-estate consolidation in its history. We closed our Newark, California campus as well as the majority of our Sunnyvale, California campus shedding 1.8 million ft2 (167,000 m2)from our real-estate portfolio. One example in this consolidation is the Software organization’s datacenter, where 32,000 ft2 (2,973 m2)of space distributed across 32 different rooms was consolidated into one 12,769 ft2 (1,186 m2) datacenter. In the end, 405 racks were configured in this space, using an average of 31.5 ft2 (2.9 m2) per rack. The initial power budget was 2 MW (out of 9 MW overall), with the ability to expand to 4 MW in the future. This design supports today's current average of 5 kW with the ability to grow to 9 kW average per rack. Keep in mind that even though the averages are 5 kW and 9 kW, racks ranging from 1 kW to 30 kW can be deployed anywhere in this datacenter.

We measured the power usage effectiveness of the Santa Clara Software organization’s datacenter, and if any single number testifies to the value of our modular design approach, it is the PUE of 1.28 that we were able to achieve. By using our modular approach, which includes using a high-efficiency variable primary-loop chiller plant, close-coupled cooling, efficient transformers, and high-efficiency UPS, an astonishing 78 percent of incoming power goes to the datacenter’s IT equipment.
Figure 4. Our Santa Clara Software organization’s datacenter achieved a PUE of 1.28, which translates to a savings of $402,652 per year compared to a target datacenter built to a PUE of 2.0.


In traditional raised floor datacenters the efficiencies worsen as densities increase. Our Pod design is efficient from day one, and remains efficient regardless of density increases.

Even though Sun compares its savings to a PUE of 2.0.  Most likely the PUE was over 2.0 given the 32 labs were scattered in conventional office spaces, not in a data center.

Note that the Santa Clara datacenter is a Tier 1 facility, by choice, with only 20 percent of the equipment on UPS. Choosing Tier 1 was a corporate decision to match the datacenter with the functions that it supports. The design approach is the same for our Tier 3 datacenters with one exception: the amount of redundancy. As you increase the redundancy (to N+1 or 2N) you can lose efficiency. If you make the correct product and
IT LoadChiller PlantRC/CRAC LoadsUPS/Transformer LossLighting78.57% PUE=1.28
16 The Range of Datacenter Requirements Sun Microsystems, Inc.
design decisions that make efficiency the highest priority, you can maintain a PUE of 1.6 or less in a Tier 3 datacenter.