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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: why read operation use so much of memory?
Date Mon, 19 Apr 2010 20:41:10 GMT
(Moving to users@ list.)

Like any Java server, Cassandra will use as much memory in its heap as
you allow it to.  You can request a GC from jconsole to see what its
approximate "real" working set it.

http://wiki.apache.org/cassandra/SSTableMemtable explains why reads
are slower than writes.  You can tune this by using the key cache, row
cache, or by using range queries instead of requesting rows one at a
time.

contrib/py_stress is a better starting place for a benchmark than
rolling your own, btw.  we see about 8000 reads/s with that on a
4-core server.

On Sun, Apr 18, 2010 at 8:40 PM, Bingbing Liu <rucbing@gmail.com> wrote:
> Hi,all
>
> I have a cluster of 5 nodes, each node has a 4 cores cpu and 8 G Memory.
>
> I use the 0.6-beta3 cassandra for testting.
>
> First , i insert 6,000,000 rows each of which is 1k bytes, the speed of write is so excited.
>
> But then ,when i read them each row at a time from two clients at the same time ,one
of the client is very slow and use so long a time,
>
> i find that on each node the process of Cassandra occupy 7 G memory or so (use the "top"
command), that puzzled me.
>
> Why read operation use so much of memory? May be i missed something?
>
> Thx.
>
>
> 2010-04-18
>
>
>
> Bingbing Liu
>

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