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The "HadoopSupport" page has been changed by jeremyhanna. http://wiki.apache.org/cassandra/HadoopSupport?action=diff&rev1=21&rev2=22 -------------------------------------------------- }}} ==== Virtual Datacenter ==== - One thing that many have asked about is whether Cassandra with Hadoop will be usable from a random access perspective. For example, you may need to use Cassandra for serving web latency requests. You may also need to run analytics over your data. In Cassandra 0.7+ there is the NetworkTopologyStrategy which allows you to customize your cluster's replication strategy by datacenter. What you can do with this is create a 'virtual datacenter' to separate nodes that serve data with high random-read performance from nodes that are meant to be used for analytics. You need to have a snitch configured with your topology and then according to the datacenters defined there (either explicitly or implicitly), you can indicate how many replicas you would like in each datacenter. You would install task trackers on nodes in your analytics section and make sure that a replica is written to that 'datacenter' in your NetworkTopologyStrategy configuration. The practical upshot of this is your analytics nodes always have current data and your high random-read performance nodes always serve data with predictable performance. + One thing that many have asked about is whether Cassandra with Hadoop will be usable from a random access perspective. For example, you may need to use Cassandra for serving web latency requests. You may also need to run analytics over your data. In Cassandra 0.7+ there is the !NetworkTopologyStrategy which allows you to customize your cluster's replication strategy by datacenter. What you can do with this is create a 'virtual datacenter' to separate nodes that serve data with high random-read performance from nodes that are meant to be used for analytics. You need to have a snitch configured with your topology and then according to the datacenters defined there (either explicitly or implicitly), you can indicate how many replicas you would like in each datacenter. You would install task trackers on nodes in your analytics section and make sure that a replica is written to that 'datacenter' in your !NetworkTopologyStrategy configuration. The practical upshot of this is your analytics nodes always have current data and your high random-read performance nodes always serve data with predictable performance. For an example of configuring Cassandra with Hadoop in the cloud, see the [[http://github.com/digitalreasoning/PyStratus|PyStratus]] project on Github.
