[Hadoop Wiki] Update of "MachineScaling" by enis

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The following page has been changed by enis:
http://wiki.apache.org/hadoop/MachineScaling

The comment on the change is:
Refactor ECC part, emphesize ECC 

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  '''More specifics:'''
  
- Hadoop benefits greatly from ECC memory, which is not low-end. Multi-core boxes tend to give more computation per dollar, per watt and per unit of operational maintenance. But the highest clockrate processors tend to not be cost-effective, as do the very largest drives. So moderately high-end commodity hardware is the most cost-effective for Hadoop today.
+ Multi-core boxes tend to give more computation per dollar, per watt and per unit of operational maintenance. But the highest clockrate processors tend to not be cost-effective, as do the very largest drives. So moderately high-end commodity hardware is the most cost-effective for Hadoop today.
  
  Some users use cast-off machines that were not reliable enough for other applications. These machines originally cost about 2/3 what normal production boxes cost and achieve almost exactly 1/2 as much. Production boxes are typically dual CPU's with dual cores.
  
  '''RAM:'''
  
  Many users find that most hadoop applications are very small in memory consumption. Users tend to have 4-8 GB machines with 2GB probably being too little.
+ Hadoop benefits greatly from ECC memory, which is not low-end, however using ECC memory is RECOMMENDED. see Dennis Kubes' discussion at http://mail-archives.apache.org/mod_mbox/hadoop-core-dev/200705.mbox/%3C465C3065.9050501@dragonflymc.com%3E