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From Peter Schuller <peter.schul...@infidyne.com>
Subject Re: Row Cache Heap Requirements (Cassandra 1.0)
Date Fri, 28 Oct 2011 13:26:48 GMT
> Is it possible, that single row (8 columns) can allocate about 2KB heap?

It sounds a bit much, though not extremely so (depending on how much
overhead there is per-column relative to per-row). Are you definitely
looking at the live size of the heap (for example, trigger a full GC
and look at results) and not just how much data there happens to be on
the heap after your insertion?

In any case, if you are looking for better memory efficiency I advise
looking at the off-heap row cache
(http://www.datastax.com/dev/blog/whats-new-in-cassandra-1-0-improved-memory-and-disk-space-management).
It is suposed to be enabled by default. If it's not, do you have JNA
installed?

The reason I say that is that the off-heap cache stores serialized
information on the heap rather than the full tree of Java objects. If
off-heap caching is enabled, 2 kb/row key would be far far more than
expected (unless I'm missing something, I've actually yet to actually
measure it myself ;)).

-- 
/ Peter Schuller (@scode, http://worldmodscode.wordpress.com)

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