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From Brandon Williams <dri...@gmail.com>
Subject Re: row cache vs frequent row updates vs write through row cache
Date Fri, 05 Nov 2010 18:49:38 GMT
On Fri, Nov 5, 2010 at 1:41 PM, Jeremy Davis
<jerdavis.cassandra@gmail.com>wrote:

> I saw in the Riptano "Tuning Cassandra" slide deck that the row cache can
> be detrimental if there are a lot of updates to the cached row. Is this
> because the cache is not write through, and every update necessitates
> creation of a new row?
> I see there is an open issue:
> https://issues.apache.org/jira/browse/CASSANDRA-860  for implementing
> write through in 0.8.


The problem is that if the row is being updated a lot, the cache is turning
over quickly, and this exerts GC pressure on the JVM.  Even if it were
write-through, row cache is probably a bad match for this kind of row, it's
much better at mostly static rows.  Rely on keycache and OS file cache for
these instead.

-Brandon

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