[Cassandra Wiki] Update of "ArchitectureOverview" by JingguoYao

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The "ArchitectureOverview" page has been changed by JingguoYao.
http://wiki.apache.org/cassandra/ArchitectureOverview?action=diff&rev1=10&rev2=11

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  write replica count > replication factor).
  
  
- You get consistency if R + W > N, where R is the number of records to read, W is the number of records to write, and N is the replication factor.  A ConsistencyLevel of ONE means R or W is 1.  A ConsistencyLevel of QUORUM means R or W is ceiling((N+1)/2).  A ConsistencyLevel of ALL means R or W is N.  So if you want to write with a ConsistencyLevel of ONE and then get the same data when you read, you need to read with ConsistencyLevel ALL.
+ You get consistency if R + W > N, where R is the number of records to read, W is the number of records to write, and N is the replication factor.  A ConsistencyLevel of ONE means R or W is 1.  A !ConsistencyLevel of QUORUM means R or W is ceiling((N+1)/2).  A !ConsistencyLevel of ALL means R or W is N.  So if you want to write with a !ConsistencyLevel of ONE and then get the same data when you read, you need to read with !ConsistencyLevel ALL.