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From Brian Frank Cooper <coop...@yahoo-inc.com>
Subject RE: Cassandra versus HBase performance study
Date Thu, 04 Feb 2010 00:45:42 GMT
0.5 does seem to be significantly faster - the latency is better and it provides significantly
more throughput. I'm updating my charts with new values now.

One thing that is puzzling is the scan performance. The scan experiment is to scan between
1-100 records on each request. My 6 node Cassandra cluster is only getting up to about 230
operations/sec, compared to >1400 ops/sec for other systems. The latency is quite a bit
higher. A chart with these results is here:

http://www.brianfrankcooper.net/pubs/scans.png

Is this the expected performance? I'm using the OrderPreservingPartitioner with InitialToken
values that should evenly partition the data (and the amount of data in /var/cassandra/data
is about the same on all servers). I'm using get_range_slice() from Java (code snippet below).


At the max throughput (230 ops/sec), when latency is over 1.2 sec, CPU usage varies from ~5%
to ~72% on different boxes. Disk busy varies from 60% to 90% (and the machine with the busiest
disk is not the one with highest CPU usage.) Network utilization (eth0 %util both in and out)
varies from 15%-40% on different boxes. So clearly there is some imbalance (and the workload
itself is skewed via a Zipfian distribution) but I'm surprised that the latencies are so high
even in this case.

Code snippet - fields is a Set<String> listing the columns I want; recordcount is the
number of records to return.

SlicePredicate predicate;
if (fields==null)
{
	predicate = new SlicePredicate(null,new SliceRange(new byte[0], new byte[0],false,1000000));
}
else
{
	Vector<byte[]> fieldlist=new Vector<byte[]>();
	for (String s : fields)
	{
		fieldlist.add(s.getBytes("UTF-8"));
	}
	predicate = new SlicePredicate(fieldlist,null);
}
ColumnParent parent = new ColumnParent("data", null);
		
List<KeySlice> results = client.get_range_slice(table,parent,predicate,startkey,"",recordcount,ConsistencyLevel.ONE);
			
Thanks!

Brian

________________________________________
From: Brian Frank Cooper
Sent: Saturday, January 30, 2010 7:56 AM
To: cassandra-user@incubator.apache.org
Subject: RE: Cassandra versus HBase performance study

Good idea, we'll benchmark 0.5 next.

brian

-----Original Message-----
From: Jonathan Ellis [mailto:jbellis@gmail.com]
Sent: Friday, January 29, 2010 1:13 PM
To: cassandra-user@incubator.apache.org
Subject: Re: Cassandra versus HBase performance study

Thanks for posting your results; it is an interesting read and we are
pleased to beat HBase in most workloads. :)

Since you originally benchmarked 0.4.2, you might be interested in the
speed gains in 0.5.  A couple graphs here:
http://spyced.blogspot.com/2010/01/cassandra-05.html

0.6 (beta in a few weeks?) is looking even better. :)

-Jonathan

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