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From Julie <julie.su...@nextcentury.com>
Subject Re: cassandra out of heap space crash
Date Fri, 11 Jun 2010 15:14:37 GMT
Ran Tavory <rantav <at> gmail.com> writes:

> 
> I can't say exactly how much memory is the correct amount, but surely 1G is
very little. By replicating 3 times your cluster now makes 3 times more work
than it used to do, both on reads and on writes while the readers/writers
continue hammering it the same pace.
> 
> 
> So once you've upped your memory (try 4g, if not enough 8g etc) if this still
doesn't help, you want to look at either adding capacity or slowing down your
writes. 
> Which consistency level are you writing with? You can try ALL, this will slow
down your writes just as much needed by the cluster to catch its breath (or so I
hope, I never actually tried that...)



Thank you so much, Ran!  I am running on ec2-smalls and they have only 1.7GB 
of memory in total so 1GB of heap space is probably the highest I can go until
we move to larger VMs.  But you bring up an EXCELLENT point -- changing the
consistency level.  Because we are trying to populate the database as quickly
as possible for our prototyping work, we use consistency of ZERO(!) I am going
to try changing it to ALL as you suggest and also possibly throttle the writes. 

Does this seem like a Cassandra bug or is it well known that Cassandra always 
needs more than 1GB of heap space?

Thanks again for your help,
Julie




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