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From dir dir <sikerasa...@gmail.com>
Subject Re: why read operation use so much of memory?
Date Tue, 20 Apr 2010 03:28:10 GMT
Hi Jonathan,

I see this page (http://wiki.apache.org/cassandra/SSTableMemtable) does not
exist yet.

thanks.

Dir.

On Tue, Apr 20, 2010 at 3:41 AM, Jonathan Ellis <jbellis@gmail.com> wrote:

> (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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