Correction to lecture: signal strength vs distance

First (and certainly not the last) mea culpa update: I goofed the discussion of the signal strength of an isotropic radiator ("perfect antenna") in class today. The signal strength degrades with the surface area of the sphere (d^2), not the volume - which is why the path loss exponent in free space is 2.
(This correction provided courtesy of the hawk-eyed Charlie Garrod. Thanks, Charlie!)

Low-Temperature Computing

Perhaps antithetical to 15-849, if you happen to have 500 liters of liquid helium to spare, you could try running your CPU at 6.5Ghz at -232 degrees C. But in keeping with what we saw with DVFS, they had to boost the CPU core voltage from about 1.15V to 1.85V. AMD did not provide comment on the PUE of a datacenter running on liquid helium.

Sun unveils new energy efficient datacenter in Colorado

According to a Sun press release, they've completed the largest datacenter consolidation project in the company's history -- which they expect to save $1M in electricity costs, and 11,000 metric tons of CO2 per year. More details in the linked article, but the datacenter uses flywheel-based UPSes, a high-end Liebert XD cooling system that can dynamically allocate the amount of cooling based on demand. (Note the little air hoods over each rack.)

The major focus seems to be on space and cooling efficiency, estimating a PUE of about 1.38. (For every 1 W of computing power, 1.38 W of power enters the datacenter.) For interesting comparison, Google claims a PUE of 1.21 across six datacenters, with one running at 1.13. It's quite likely that some of those datacenters use evaporative cooling in friendly environments, etc.

'Net uses more power, more efficiently

Earth2Tech quotes a report from LBL that explores the growth in Internet energy use (doubling from 2000 to 2006), vs. Internet traffic (increasing by about 22x in the same time period). A few interesting numbers, like claims that DSL uses 0.17 kWh per gigabyte --- not counting the power draw of your computer, of course.

Rackable's "MicroSlice" arrays

Companies are starting to introduce products similar to our own research on Fast Arrays of Wimpy Nodes that exploit the idea of packing more smaller computers into a single enclosure. The commercial offerings are much less radical than some of the proposed research designs, but should experience some of the benefits anyway. James Hamilton, now at Amazon, has a nice post to his (very worthwhile) blog about low cost, low-power servers. The techtarget article attributes to Rackable a statement about getting rid of the need for virtualization, but I suspect that the technologies will remain complimentary.

Symantec: Data Center Managers Pressured to "Do More with Less"

Symantec's State of the Data Center Report (PR article from Symantec):

The second annual study found that data center managers are caught between two conflicting goals – more demanding user expectations and higher levels of performance, yet reducing costs remain the primary objective for the data center. The report also found that data center staffing remains problematic, servers and storage continue to be underutilized and disaster recovery plans are out of date. Finally, the respondents indicated that while they are pursuing green data center initiatives, they are doing so primarily based on cost benefits.

And notes that they're attempting to do so using familiar-sounding tools:

The major server-related initiatives include server consolidation (80 percent) and server virtualization (77 percent).

Or see the full PDF version of the 2008 State of the Data Center report (pdf)

Intel articles about low-power CPU states

Anshul writes with two relevant links for low power states in CPUs:

2006 article about P and C states in Intel processors.

The second article talks about the C1E (extended HLT) state, (Page 6) which is like normal C1 but also turns voltage down to the lowest level. This type of sleep state may address some of the issues of using idle states in the first two papers we read this semester.

Cisco entering virtual server market

Relevant to today's readings in virtualization for cluster energy savings: Cisco Plans Big Push into Server Market.

“Our vision is, how do we virtualize the entire data center?” Ms. Warrior said. “It is not about a single product. We will have a series of products that enable us to make that transition.”