When Region Servers are co-located with Datanodes, you can utilize short
circuit read feature.
See 12.11.2 of http://hbase.apache.org/book.html#perf.hdfs

Factors to consider co-location include the allocation of memory of server
- so that region server and Data node can have ample memory to fulfill
their tasks.

Cheers
On Mon, Apr 14, 2014 at 8:59 PM, Shashidhar Rao
<[EMAIL PROTECTED]>wrote:
 
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