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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Ec2 Stress Results
Date Sat, 07 May 2011 02:47:12 GMT
On Fri, May 6, 2011 at 5:13 PM, Alex Araujo
<cassandra-users@alex.otherinbox.com> wrote:
> I raised the default MAX_HEAP setting from the AMI to 12GB (~80% of
> available memory).

This is going to make GC pauses larger for no good reason.

> raised
> concurrent_writes to 300 based on a (perhaps arbitrary?) recommendation in
> 'Cassandra: The Definitive Guide'

That's never been a good recommendation.

> Based on the above, would I be correct in assuming that frequent memtable
> flushes and/or commitlog I/O are the likely bottlenecks?

Did I miss where you said what CPU usage was?

How many replicas are you writing?

Recent testing suggests that putting the commitlog on the raid0 volume
is better than on the root volume on ec2, since the root isn't really
a separate device.

-- 
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of DataStax, the source for professional Cassandra support
http://www.datastax.com

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