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From Apache Wiki <>
Subject [Cassandra Wiki] Trivial Update of "MemtableThresholds" by FlipKromer
Date Tue, 31 Aug 2010 02:28:09 GMT
Dear Wiki user,

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The "MemtableThresholds" page has been changed by FlipKromer.
The comment on this change is: removed duplicate sentence.


  == Memtable Thresholds ==
  When performing write operations, Cassandra stores values to column-family specific, in-memory
data structures called Memtables. These Memtables are flushed to disk whenever one of the
configurable thresholds is exceeded. Proper tuning of these thresholds is important in making
the most of  available system memory, without bringing the node down for lack of memory.
- (Note that by default bin/ specifies a maximum JVM heap of -Xmx1G, which
is very low for production use.  Consider increasing this as well.)
  == Configuring Thresholds ==
  Since Memtables are storing actual column values, they consume at least as much memory as
the size of data inserted. However, there is also overhead  associated with the structures
used to index this data. When the number of columns and rows is high compared to the size
of values, this overhead can become quite significant, (possibly greater than the data itself).

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