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The "LargeDataSetConsiderations" page has been changed by PeterSchuller. The comment on this change is: Reflect that 1878 was fixed for 0.6.9 and 0.7.0. http://wiki.apache.org/cassandra/LargeDataSetConsiderations?action=diff&rev1=15&rev2=16 -------------------------------------------------- * Repair operations can increase disk space demands (particularly in 0.6, less so in 0.7; TODO: provide actual maximum growth and what it depends on). * As your data set becomes larger and larger (assuming significantly larger than memory), you become more and more dependent on caching to elide I/O operations. As you plan and test your capacity, keep in mind that: * The cassandra row cache is in the JVM heap and unaffected (remains warm) by compactions and repair operations. This is a plus, but the down-side is that the row cache is not very memory efficient compared to the operating system page cache. - * The key cache is affected by compaction because it is per-sstable, and compaction moves data to new sstables. + * For 0.6.8 and below, the key cache is affected by compaction because it is per-sstable, and compaction moves data to new sstables. - * Soon no longer true as of: [[https://issues.apache.org/jira/browse/CASSANDRA-1878|CASSANDRA-1878]] + * Was fixed/improved as of [[https://issues.apache.org/jira/browse/CASSANDRA-1878|CASSANDRA-1878]], for 0.6.9 and 0.7.0. * The operating system's page cache is affected by compaction and repair operations. If you are relying on the page cache to keep the active set in memory, you may see significant degradation on performance as a result of compaction and repair operations. * Potential future improvements: [[https://issues.apache.org/jira/browse/CASSANDRA-1470|CASSANDRA-1470]], [[https://issues.apache.org/jira/browse/CASSANDRA-1882|CASSANDRA-1882]]. * If you have column families with more than 143 million row keys in them, bloom filter false positive rates are likely to go up because of implementation concerns that limit the maximum size of a bloom filter. See [[ArchitectureInternals]] for information on how bloom filters are used. The negative effects of hitting this limit is that reads will start taking additional seeks to disk as the row count increases. Note that the effect you are seeing at any given moment will depend on when compaction was last run, because the bloom filter limit is per-sstable. It is an issue for column families because after a major compaction, the entire column family will be in a single sstable.
