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From Chris Goffinet>
Subject Re: Size calculations for off heap caching
Date Wed, 19 Oct 2011 03:40:46 GMT
My best advice on this is, insert a bit of data into the tree, and then do a
heap dump to calculate the extra overhead. It's unfortunately more than you
would like from our testing.

On Tue, Oct 18, 2011 at 8:14 PM, Todd Nine <> wrote:

> **
> 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?
> Thanks,
> Todd

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