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The "LargeDataSetConsiderations" page has been changed by PeterSchuller. http://wiki.apache.org/cassandra/LargeDataSetConsiderations?action=diff&rev1=5&rev2=6 -------------------------------------------------- * 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. * There is work happening to improve this. TODO: link to JIRA tickets about direct i/o, fadvise, mincore() etc. * 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. - * This will likely be addressed in the future: TODO: add JIRA links to the bigger-bf and the limit-sstable-size issue. + * This will likely be addressed in the future: See [[https://issues.apache.org/jira/browse/CASSANDRA-1608|CASSANDRA-1608]] and TODO: bigger-bf jira * Compaction is currently not concurrent, so only a single compaction runs at a time. This means that sstable counts may spike during larger compactions as several smaller sstables are written while a large compaction is happening. This can cause additional seeks on reads. * TODO: link to parallel compaction JIRA ticket, file another one specifically for ensuring this issue is addressed (the pre-existing only deals with using multiple cores for throughput reasons) * Consider the choice of file system. Removal of large files is notoriously slow and seek bound on e.g. ext2/ext3. Consider xfs or ext4fs.
