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From Matthias Zeilinger <>
Subject RE: multiple Datacenter values in PropertyFileSnitch
Date Fri, 12 Apr 2013 05:57:00 GMT
I´m using for each application it´s own keyspace.
What I want is to split up for different load patterns.
So that 2 apps with same and very high load pattern are not clashing.

For other load patterns I want to use another splitting.

Is there any best practice or should I scale out, so that the complete load can be distributed
to on all nodes?

Matthias Zeilinger
Production Operation - Shared Services

P: +43 (0) 50 858-31185
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From: aaron morton []
Sent: Donnerstag, 11. April 2013 20:48
Subject: Re: multiple Datacenter values in PropertyFileSnitch

A node can only exist in one DC and one rack.

Use different keyspaces as suggested.


Aaron Morton
Freelance Cassandra Consultant
New Zealand


On 12/04/2013, at 1:47 AM, Jabbar Azam <<>>


I'm not an expert but I don't think you can do what you want. The way to separate data for
applications on the same cluster is to use different tables for different applications or
use multiple keyspaces, a keyspace per application. The replication factor you specify for
each keyspace specifies how many copies of the data are stored in each datacenter.
You can't specify that data for a particular application is stored on a specific node, unless
that node is in its own cluster.
I think of a cassandra cluster as a shared resource where all the applications have access
to all the nodes in the cluster.


Jabbar Azam

On 11 April 2013 14:13, Matthias Zeilinger <<>>

I would like to create big cluster for many applications.
Within this cluster I would like to separate the data for each application, which can be easily
done via different virtual datacenters and the correct replication strategy.
What I would like to know, if I can specify for 1 node multiple values in the PropertyFileSnitch
configuration, so that I can use 1 node for more applications?
For example:
6 nodes:
3 for App A
3 for App B
4 for App C

I want to have such a configuration:
Node 1 - DC-A& DC-C
Node 2 - DC-B & DC-C
Node 3 - DC-A & DC-C
Node 4 - DC-B & DC-C
Node 5 - DC-A
Node 6 - DC-B

Is this possible or does anyone have another solution for this?

Thx & br matthias

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