http://www.datastax.com/support-forums/topic/incorrect-replica-assignment Software, Support, and Training for Apache Cassandra en-US Wed, 22 May 2013 17:47:51 +0000 http://bbpress.org/?v=1.0.3 q http://www.datastax.com/support-forums/search.php http://www.datastax.com/support-forums/topic/incorrect-replica-assignment#post-7489 Tue, 13 Nov 2012 20:07:59 +0000 fredespi 7489@http://www.datastax.com/support-forums/ <p>Unfortunately I had already switched tokens between two of the nodes so I can't replicate the problem now. Sorry. </p> http://www.datastax.com/support-forums/topic/incorrect-replica-assignment#post-7435 Wed, 07 Nov 2012 23:30:15 +0000 nickmbailey 7435@http://www.datastax.com/support-forums/ <p>That could perhaps be a bug. Can you attach the output from 'nodetool ring' and 'nodetool describering &lt;keyspace&gt;' </p> http://www.datastax.com/support-forums/topic/incorrect-replica-assignment#post-7433 Wed, 07 Nov 2012 20:42:11 +0000 fredespi 7433@http://www.datastax.com/support-forums/ <p>using opscenter view replication and by doing nodetool describering keyspace. </p> http://www.datastax.com/support-forums/topic/incorrect-replica-assignment#post-7432 Wed, 07 Nov 2012 19:36:21 +0000 nickmbailey 7432@http://www.datastax.com/support-forums/ <p>How are you determining where data is being replicated? </p> http://www.datastax.com/support-forums/topic/incorrect-replica-assignment#post-7431 Wed, 07 Nov 2012 19:29:02 +0000 fredespi 7431@http://www.datastax.com/support-forums/ <p>NetworkTopologyStrategy with a cassandra-topology.properties. </p> http://www.datastax.com/support-forums/topic/incorrect-replica-assignment#post-7400 Mon, 05 Nov 2012 16:51:22 +0000 nickmbailey 7400@http://www.datastax.com/support-forums/ <p>Are you using SimpleStrategy or NetworkTopologyStrategy for your keyspace? </p> http://www.datastax.com/support-forums/topic/incorrect-replica-assignment#post-7375 Fri, 02 Nov 2012 16:15:11 +0000 fredespi 7375@http://www.datastax.com/support-forums/ <p>I read this post: <a href="http://www.datastax.com/support-forums/topic/is-networktopology-strategy-unbalanced#post-1391" rel="nofollow">http://www.datastax.com/support-forums/topic/is-networktopology-strategy-unbalanced#post-1391</a></p> <p>And documentation I've read elsewhere agrees with this post: within a dc replicas will be assigned according to the hash key and then around the ring, skipping the same rack. But I am not seeing this.</p> <p>I start with a 2 node dc with 2 racks. These nodes are in fact virtual machines on two separate physical machines. Tokens are assigned with 0 and 85070591730234615865843651857942052864, for node 1 on rack1 and 2 on rack2 respectively. RF is 2. Nodes replicate to each other. And that's the point; my idea is to replicate across racks and thereby physical machines.</p> <p>I then expand the cluster with 2 more nodes, one in each rack. The 2 new tokens that split the keyspaces in half are assigned to the new nodes: 42535295865117307932921825928971026432 to new node on rack 1 and 127605887595351923798765477786913079296 to new node on rack 2. In the ring (i.e. the token order) the first node is still the first, the new node in rack1 is now number 2, the old second node in rack2 is now number 3, and the new node in rack 2 is number 4.</p> <p>After waiting for bootstrapping I find that node 1 now replicates to node 2 (same rack), node 2 to node 3 (across to the other rack), node 3 to node 4 (same rack), and node 4 to node 1 (across). This is not what I wanted or expected. I expected a key to get it's first replica in the node to which the key belongs (for example node1). Then the next replica would be the next in the ring which is not in the same rack. In this case that would be node 3 in rack2. </p> <p>So I try to change the token assignements around. That's something I really would like to avoid since the old nodes have accumulated quite a bit of data. I switch tokens between node 2 on rack 1 and node 3 on rack 2. Now replication works as I want, across racks, and I believe that both racks now contain the full data so that I have fault tolerance and can loose a whole rack and still have all data. But it seems it's because replication simply follows the token order around the ring. </p> <p>What am I missing? </p>