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From onmstester onmstester <>
Subject Re: Cassandra cluster: could not reach linear scalability
Date Sun, 18 Feb 2018 15:40:36 GMT
I'm running tests on separate machine (not member of the cluster)

I'm using the default data model of cassandra-stress tool : keyspace1 and table: standard1.
nothing special on network or data traffic. Network capable of 1 G and tested it with ipperf.

iftop shows maximum of 48Mbit traffic between nodes in cluster.

Have not seen any warning in log files.

I'm monitoring cassandra during runtime using jvisual vm and never saw any GC chokepoints,
cpu is below 40% always. I just cant understand why cassandra is limmiting the throughput?!

using top, fps and write per seconds are not showing any problems

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---- On Sun, 18 Feb 2018 18:42:48 +0330 Rahul Singh &lt;;
wrote ----

Got it.


 Here are some other questions.


 Are you running the test on separate machine or one of the cluster members?


 When configuring Cassandra stress what data model did you end up using? ( do you see Data
or traffic skew?)


 Do you see any wide partitions or Tombstone warnings on either node.


 Have you visualized the GC logs using something like VisualVM or hubspots GC visualizer?
This is to see if there are chokepoints in the GC cycle.



 Rahul Singh


 Anant Corporation

On Feb 18, 2018, 9:23 AM -0500, onmstester onmstester &lt;;,

But monitoring cassandra with jmx using jvisualVM shows no problem, less than 30% of heap
size used

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---- On Sun, 18 Feb 2018 17:26:59 +0330 Rahul Singh &lt;;
wrote ----

You don’t don’t have enough memory. That’s just a start.


Rahul Singh

Anant Corporation

On Feb 18, 2018, 6:29 AM -0500, onmstester onmstester &lt;;,

I've configured a simple cluster using two PC with identical spec:

 cpu core i5 RAM: 8GB ddr3 Disk: 1TB 5400rpm Network: 1 G (I've test it with iperf, it really
using the common configs described in many sites including datastax itself:

cluster_name: 'MyCassandraCluster' num_tokens: 256 seed_provider: - class_name: org.apache.cassandra.locator.SimpleSeedProvider
parameters: - seeds: "," listen_address: rpc_address: endpoint_snitch:
Running stress tool:

cassandra-stress write n=1000000 -rate threads=1000 -mode native cql3 -node,

Over each node it shows 39 K writes/seconds, but running the same stress tool command on cluster
of both nodes shows 45 K writes/seconds. I've done all the tuning mentioned by apache and
datastax. There are many use cases on the net proving Cassandra linear Scalability So what
is wrong with my cluster?

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