I think Dave is right, I have read this article again: http://thelastpickle.com/2011/07/04/Cassandra-Query-Plans/
I have data on two nodes, and "QUORUM read" means it need read from both two nodes. I guess I need to increase the RF to 3, to make the system can tolerance one node failure. thanks for all of the kind help! On Fri, Jul 27, 2012 at 8:08 PM, Riyad Kalla <rka...@gmail.com> wrote: > Dave, per my understanding of Yan's description he has 3 nodes and took > one down manually to test; that should have worked, no? > > > On Thu, Jul 26, 2012 at 11:00 PM, Dave Brosius > <dbros...@mebigfatguy.com>wrote: > >> Quorum is defined as >> >> (replication_factor / 2) + 1 >> therefore quorum when rf = 2 is 2! so in your case, both nodes must be up. >> >> Really, using Quorum only starts making sense as a 'quorum' when RF=3 >> >> >> >> >> >> >> On 07/26/2012 10:38 PM, Yan Chunlu wrote: >> >> I am using Cassandra 1.0.2, have a 3 nodes cluster. the consistency level >> of read & write are both QUORUM. >> >> At first the RF=1, and I figured that one node down will cause the >> cluster unusable. so I changed RF to 2, and run nodetool repair on every >> node(actually I did it twice). >> >> After the operation I think my data should be in at least two nodes, >> and it would be okay if one of them is down. >> >> But when I tried to simulate the failure, by disablegossip of one node, >> and the cluster knows this node is down. then access data from the cluster, >> it returned "MaximumRetryException"(pycassa). as my experiences this is >> caused by "UnavailableException", which is means the data it is requesting >> is on a node which is down. >> >> so I wonder my data might not be replicated right, what should I do? >> thanks for the help! >> >> here is the keyspace info: >> >> * >> * >> *Keyspace: comments:* >> * Replication Strategy: org.apache.cassandra.locator.SimpleStrategy* >> * Durable Writes: true* >> * Options: [replication_factor:2]* >> >> >> >> the scheme version is okay: >> >> *[default@unknown] describe cluster;* >> *Cluster Information:* >> * Snitch: org.apache.cassandra.locator.SimpleSnitch* >> * Partitioner: org.apache.cassandra.dht.RandomPartitioner* >> * Schema versions: * >> * f67d0d50-b923-11e1-0000-4f7cf9240aef: [192.168.1.129, 192.168.1.40, >> 192.168.1.50]* >> >> >> >> the loads are as below: >> >> *nodetool -h localhost ring* >> *Address DC Rack Status State Load >> Owns Token * >> * >> 113427455640312821154458202477256070484 * >> *192.168.1.50 datacenter1 rack1 Up Normal 28.77 GB >> 33.33% 0 * >> *192.168.1.40 datacenter1 rack1 Up Normal 26.67 GB >> 33.33% 56713727820156410577229101238628035242 * >> *192.168.1.129 datacenter1 rack1 Up Normal 33.25 GB >> 33.33% 113427455640312821154458202477256070484 * >> >> >> >
