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From Jonathan Ellis <>
Subject Re: what is taking up my JVM heap space?
Date Fri, 05 Aug 2011 02:44:58 GMT
If you didn't GC post-flush then it's just leftovers.

An "empty" Cassandra (nothing in memtables or cache) will use 5-10MB of heap.

On Thu, Aug 4, 2011 at 9:38 PM, Yang <> wrote:
> I ran my cassandra cluster on one node, inserted about 500000 rows,
> each about 400 bytes, then the heap went up to 800MB, and constantly
> goes into full GC. I guessed that the memtable was probably taking a
> lot of space, so I did a node tool flush, so that
> all memtable are changed to 0. after this, the heap came down a bit,  to 500MB.
> but I thought it should be close to 0 right after the flush?? or else
> what is taking up the space?
> I'm still trying to look at the hprof file to figure out, but it seems
> difficult too
> Thanks
> Yang

Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of DataStax, the source for professional Cassandra support

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