Cassandra minimum heap size

Question

What is the minimum recommended heap size for Cassandra? On the Cassandra wiki page we can read: "the more memory, the better, with 4GB being the minimum we typically recommended"

On the Datastax website:

"Java heap space should be set to a maximum of 8GB or half of your total RAM, whichever is lower."

But I cannot find anywhere more information on what should be the minimum recommended heap RAM. Assuming we run other services on the same server we do not want Cassandra to use half of a RAM hence we need to specify the maximum HEAP memory. Should we aim at 4GB heap as minimum or 8GB or perhaps 2GB is absolutely fine?

Answer 1

It depends a lot on your workload and amount of data. For high volume insert workloads you will need a large heap, at least 4 GB. You will probably need a larger heap for more data, although in Cassandra 2.0 (the latest version) this is less important - if you have less than 1 TB per node then there won't be much heap pressure.

The only way you can determine the heap size that works for you is to run a load test.

Answer 2

Was able to run cassandra on 400Mb heap on t2.micro EC2. No need for super-performance.