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From Todd Nine <>
Subject Size calculations for off heap caching
Date Wed, 19 Oct 2011 03:14:29 GMT
Hi guys,
  We've just built a K tree implementation in cassandra.  We're going
for relatively "wide" nodes in our tree to minimize our tree depth and
increase our search times.   Most of the links between parent/child
nodes are longs.  We're ready to start tuning the size of K so that our
most access paths in our tree will be row cached in Cassandra.  We're on
Cassandra 0.8.7, and I can't find any documentation regarding the actual
memory size of the off heap row cache.  Can someone explain how much
additional space will be used when caching rows?  For instance, if our
links between nodes are all Longs, and we have 100 children (cols), that
gives us 900 bytes with a 0 byte placeholder value.  What is the
additional overhead when using the off heap storage?


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