数据中心“着火”了

Gallon is a unit for measuring liquids, equal to eight pints. In Britain this is 4.55 litres, and in the US it is 3.79 litres.

(7+20)/2 * (4.55+3.79)/2 = 56.295万升 = 563吨

WSC:  warehouse-scale computers.

MapReduce can be thought of as a generalization of the single instruction stream, multiple data streams (SIMD) operation - except that a function to be applied is passed to the data. That is followed by a function that is used in a reduction of the output from the Map task. Because reductions are commonplace even in SIMD programs, SIMD hardware often offers special operations for the reductions. For example, Intel's AVX SIMD instructions include "horizontal" instructions that add pairs of operands that are adjacent in registers.

Here is the power usage inside the IT equipment for a Google WSC deployed in 2012 (Barroso et al., 2013):

• 42% of power for processors
• 12% for DRAM
• 14% for disks
• 5% for networking
• 15% for cooling overhead
• 8% for power overhead
• 4% miscellaneous