On Tuesday I participated in an industry panel at the 1st Int' Conf. on Energy-Efficient Computing and Networking at the University of Passau, Germany. In my introduction statement I could mention Sun's contributions only very briefly. So here some more detailed references:
In 2005/2006 Sun introduced the first generation of systems based on the CoolThreads/Chip Multithreading(CMT) Technology which offered a leading efficiency measured in performance/watt - even more considering the space requirements as well. Pacific Gas and Electric (PG&E) in California offered customers who replaced old, inefficient servers with efficient Sun servers with CoolThreads technology cash savings of up to $1,000 per server. This family has evolved and the T5440 recently was used for a new record TPC-C benchmark result which did beat the previously leading result from IBM consuming only 1/6th of the energy.
Besides energy efficient servers new storage technologies helped to achieve this result. Flash memory comes in various form factors from Flash Modules with an SO-DIMM form factor to Solid State Disk Drives (SSDs) to the F5100 Flash Arraywhich was used in the TPC-C benchmark and can deliver many more IOPS per Watt than traditional hard disk drives (HDDs) - about 4.000 Write IOPS per Watt from an F5100 versus 2.300 from an SSD versus 10 from an HDD. Yet given the limited capacity compared to HDDs makes flash not a one to one replacement - at least for now. Flash becomes a new tier in the storage hierarchy - between RAM and HDDs, but this needs to be managed. The Flash Cache feature in Oracle Database 11gR2 allows the use of Flash as a second level cache for the SGA. With Solaris ZFS flash may be used as a second level file buffer - the L2ARC - and for an intent log to to accelerate synchronous writes in a transparent manner. This concept is summarized under the term Hybrid Storage Pool emphasizing that thereby slower HDDs combined with a few SDDs can form a fast storage system. Such storage systems are sold as appliances in the Sun Open Storage product line. For long term archival tape is still the most energy efficient media. The Clipper Group stated in 2008 that tape is 290x more efficient than disk. Oracle's Sun Storage Archive Manager (SAM) - a hierarchical storage management (HSM) system - again enables the automated and transparent management of storage tier.
Not just for storage but also for servers the operating system is a key component to actually enable the use of hardware capabilities. Sun worked closely with Intel to effectively enable Solaris to use the power management features in their processors. The Power Aware Dispatcher that comes with Solaris 10 10/09 and with OpenSolaris coalesces load to power domains to enable others to reach and stay in deep sleep states. Also the cyclic 100Hz clock is being replaced by a event-driven approach to avoid waking up a core just to find out that there is no work to do. Eric Saxe's presentation (slides) from last year's OpenSolaris Developer Conference in Dresden, Germany gives an overview. These principles, e.g. that polling is a bad idea from an energy efficiency perspective, are also relevant for software higher up in the stack.
Server consolidation using visualization is a common approach to improve overall utilization in a data center. But there is also a huge potential on the desktop - from using SunRays, the Sun ultra thin client to the Oracle Desktop Infrastructure Software which provides a complete solution for managing, hosting, and providing access to virtualized desktop operating systems hosted in the datacenter.
On the datacenter level managing the airflow from the CRACs to racks has become essential, especially with racks that may consume 10 to 30 KW. The Sun Modular Datacenter "Project Blackbox" achieved 40% lower cooling costs in 1/8th the space by putting racks in containers (short video).
A hot topic these days is cloud computing which may shift load from smaller into larger, more efficient datacenters which may also be able to level out the load curves from multiple users. Sun and Oracle are of course engaged in cloud computing. There is always the Sun behind a cloud.

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