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From "Kenneth Brotman" <>
Subject RE: Slender Cassandra Cluster Project
Date Wed, 17 Jan 2018 00:24:54 GMT
Sure.  That takes the project from awesome to 10X awesome.  I absolutely would be willing to
do that.  Thanks Kurt!


Regarding your comment on the keyspaces, I agree.  There should be a few simple examples one
way or the other that can be duplicated and observed, and then an example to duplicate and
play with that has a nice real world mix, with some keyspaces that replicate over only a subset
of DC’s and some that replicate to all DC’s.


Kenneth Brotman 


From: kurt greaves [] 
Sent: Tuesday, January 16, 2018 1:31 PM
To: User
Subject: Re: Slender Cassandra Cluster Project


Sounds like a great idea. Probably would be valuable to add to the official docs as an example
set up if you're willing.


Only thing I'd add is that you should have keyspaces that replicate over only a subset of
DC's, plus one/some replicated to all DC's


On 17 Jan. 2018 03:26, "Kenneth Brotman" <> wrote:

I’ve begun working on a reference project intended to provide guidance on configuring and
operating a modest Cassandra cluster of about 18 nodes suitable for the economic study, demonstration,
experimentation and testing of a Cassandra cluster.


The slender cluster would be designed to be as inexpensive as possible while still using real
world hardware in order to lower the cost to those with limited initial resources. Sorry no
Raspberry Pi’s for this project.  


There would be an on-premises version and a cloud version.  Guidance would be provided on
configuring the cluster, on demonstrating key Cassandra behaviors, on files sizes, capacity
to use with the Slender Cassandra Cluster, and so on.


Why about eighteen nodes? I tried to figure out what the minimum number of nodes needed for
Cassandra to be Cassandra is?  Here were my considerations:


•             A user wouldn’t run Cassandra in just one data center; so at least two datacenters.

•             A user probably would want a third data center available for analytics.

•             There needs to be enough nodes for enough parallelism to observe Cassandra’s
distributed nature.

•             The cluster should have enough nodes that one gets a sense of the need for
cluster wide management tools to do things like repairs, snapshots and cluster monitoring.

•             The cluster should be able to demonstrate a RF=3 with local quorum.  If replicated
in all three data centers, one write would impact half the 18 nodes, 3 datacenters X 3 nodes
per data center = 9 nodes of 18 nodes.  If replicated in two of the data centers, one write
would still impact one third of the 18 nodes, 2 DC’s X 3 nodes per DC = 6 of the 18 nodes.


So eighteen seems like the minimum number of nodes needed.  That’s six nodes in each of
three data centers.


Before I get too carried away with this project, I’m looking for some feedback on whether
this project would indeed be helpful to others? Also, should the project be changed in any


It’s always a pleasure to connect with the Cassandra users’ community.  Thanks for all
the hard work, the expertise, the civil dialog.


Kenneth Brotman

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