It If you only have 100 partitions, then having more than (100 * RF) nodes 
doesn’t help you much.


However, unless you’re using very specific partitioners, there’s no guarantee 
that you’ll have 1 partition per node (with 10 nodes / 10 partitions).


Cassandra uses murmur3 hash (by default, and md5 in old versions) to hash the 
partition key to place data onto a node. You have very little control over 
distribution – murmur3 and md5 are both sufficiently distributed that you’re 
likely to have a good distribution on sufficiently high number of partitions, 
but with 100 partitions, you’re going to have a miserable time.


If your data model is such that you’re only ever going to have 100 partitions, 
your data model is broken, or you should use some other database. 




From: S Ahmed <>
Reply-To: "" <>
Date: Wednesday, September 21, 2016 at 2:40 PM
To: "" <>
Subject: understanding partitions and # of nodes




If you have a 10 node cluster, how does having 10 partitions or 100 partitions 
change how cassandra will perform?


With 10 partitions you will have 1 partition per node.

WIth 100 partitions you will have 10 partitions per node.


With 100 partitions I guess it helps because when you add more nodes to your 
cluster, the data can be redistributed since you have more nodes.


What else are things to consider?



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