Hbase block size

[Job Thomas]

Hi all ,
 
  
  Please tell me how to set Hbase block size in hbase-site.xml .
  I am using HBase 0.94.12 with hadoop 1.0.4 .
  I have red that by setting block size to small value(say 8 kb ) , we can 
improve habse random read.
  Is that currect? How that property affect the performance improvement if that 
is right?
 
With  Thank for all support till now,
 
Best Regards,
Job M Thomas