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From Anthony Wilcox <peacepatr...@hotmail.com>
Subject RE: Immutable CFs and read consistency
Date Fri, 07 Oct 2011 13:32:31 GMT

The last sentence should have been "In other words, does R apply also to (possibly failed)
read attempts or only to successful reads?"

 Anthony

From: peacepatriot@hotmail.com
To: user@cassandra.apache.org
Subject: Immutable CFs and read consistency
Date: Fri, 7 Oct 2011 06:21:04 -0700








We have a Column Family that is immutable (no updates after the first write).  Suppose we
use RF=2 and W=1.  Do we still need R=2, so that R+W>RF?  Or is it sufficient to have R=1?
 My guess is yes, R=1 is sufficient since if it reads a row, the row has to be correct: it
can't get stale data.     But can it get NO data? That is, with R=1 might cassandra look on
one of the two nodes, find no data there, and prematurely give up?  In other words, does R
apply only to (possibly failed) read attempts or only to successful reads?

 Thanks, Anthony
 		 	   		   		 	   		  
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