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From "Blew, Aaron" <>
Subject RackAwareStrategy Documentation Disparity
Date Fri, 11 Jun 2010 17:34:10 GMT
I was browsing the docs for the RackAware replication strategy and saw this on the wiki:

"RackAwareStrategy: replica 2 is placed in the first node along the ring the belongs in another
data center than the first; the remaining N-2 replicas, if any, are placed on the first nodes
along the ring in the *same* rack as the first"

However the storage.conf comments say the following:
"Strategy: Setting this to the class that implements IReplicaPlacementStrategy will change
the way the node picker works.  Out of the box, Cassandra provides org.apache.cassandra.locator.RackUnawareStrategy
and org.apache.cassandra.locator.RackAwareStrategy (place one replica in a different datacenter,
and the others on different racks in the same one.)"

To me the comments in storage.conf make more sense since you'd want datacenter diversity for
the data as well as rack level diversity within the local datacenter.  Which one is accurate?
 Is the disparity a result of the wiki page not being updated after the behavior changed with
a release?

Thanks all,

Aaron Blew -
Sr. Infrastructure Engineer | The Automator
iovation - The Power of Reputation™

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Portland, OR 97204

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