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From Samuel Benz <>
Subject quorum calculation seems to depend on previous selected nodes
Date Mon, 17 Jan 2011 15:55:24 GMT
Dear List

I found a strange behavior on our mini cluster during update with
consistency level quorum.

We have a cluster with 4 nodes. ReplicationFactor is 2, ReplicaPlacment
is the RackAwareStrategy and the EndpointSnitch is the
PropertyFileEndpointSnitch (with two data center and two racks each).

My understanding is, that with this parameter of the cluster, it should
be possible to update with consistency level quorum while one data
center (two nodes) are shutdown completely.

During testing I observed that this is not in every case true. It
depends on the node on which you are connected for the update. Let me
explain this more detailed:

During the tests only Node1 (D1R1) and Node2 (D1R2) are up and running.
Node3 (D2R1) and Node4 (D2R2) are shutdown. In both tests I'm connected
to Node1 and update the row: 'TEST'.

If 'TEST' was previous stored on Node1, Node2, Node3 -> The update will

If 'TEST' was previous stored on Node2, Node3, Node4 -> The update will
not work.

In both case at least two nodes, which are required for quorum, are
alive. So is this a bug or is my interpretation of the cluster
parameters wrong?


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