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From Eran Kutner <e...@gigya.com>
Subject Questions while evaluating Cassandra
Date Tue, 02 Mar 2010 12:43:47 GMT
Hi,
I'm evaluating Cassandra and really like its simplicity and ease of
maintenance compared to my other alternative which is HBase. While comparing
the two products a few questions came up which I couldn't find answers to:

   1. Is the procedure described in the description of ticket
*CASSANDRA-44<http://issues.apache.org/jira/browse/CASSANDRA-44>
   * really the way to do schema changes in the latest release? I'm not sure
   what's your thoughts about this but our experience is that every release of
   our software requires schema changes because we add new column families for
   indexes.
   Just as a note. The HBases way of managing schema seems to make much more
   sense than keeping it in configuration files that have to be deployed to all
   the nodes in the cluster. Any idea on the timeframe for 0.7?
   2. Our application needs a lot of range scans. Is there anything being
   done to improve the poor range scan performance as reflected here:
   http://www.brianfrankcooper.net/pubs/ycsb-v4.pdf ?
   3. What is the reason for the replication strategy with two DCs? As far
   as I understand it means that only one replica will exist in the second DC.
   It also means that quorum reads will fail when attempted on the second DC
   while the first DC is down. Am I missing something?
   4. Are there any plans to have a inter-cluster replication option? I mean
   having two clusters running in two DCs, each will be stand alone but they
   will replicate data between themselves. This can avoid the problem mentioned
   above, as well as avoid the high cost of inter-DC traffic when doing
   Read-Repairs for every read.
   5. From everything I've read I didn't understand if load balancing is
   local or global. In other words, what happens exactly when a new node is
   added? Will it only balance its two neighbors on the ring or will the
   re-balance propagate through the ring and all the nodes will be rebalanced
   evenly?
   6. I see that Hadoop support is coming in 0.6 but from following the
   ticket on Jira
(*CASSANDRA-342<http://issues.apache.org/jira/browse/CASSANDRA-342>
   )* I didn't understand if it will support the orderPreservingPartitioner
   or not.
   7. Do the clients have to be recompiled and deployed when a new version
   of Cassandra is deployed, or are new releases backward compatible?

Thanks for your help.

Eran Kutner,
Gigya

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