# How to choose number of executors required for our cluster ?

Let's consider it is a "20 Node Cluster"

Each Node (30 Cores , 128GB RAM

* For good throughput let's assign 5 CORES per EXECUTOR
    
    \--executor-cores = 5
    
* Should leave 1 core for Background activity (Hadoop/Yarn daemons) Number of cores available = 30 -1 = 29
    
* Total available of cores in cluster = 29\*20 =580
    
* Number of executors in cluster  
    \= total cores per cluster / no.of cores per executors  
    \= 580/5 = 116
    
* Should leave 1 executor for Yarn (Application Manager)  
    Now available executors in cluster = 116 - 1 = 115
    
* Number of executors per node = 116/20 = 6 (approx)
    
* Memory per executor = 128GB /6 = 21 GB  
    7% of 21 GB approximately 1.5 GB will be allocated to heap overhead.
    
* Now actual --executor-memory = 21GB - 2GB = 19 GB per executor.  
      
    So, recommended  
    **116 Executors (19 GB Memory, 5 cores) for "20 Node Cluster".**
    

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739779766955/ffaa9969-12fa-49f3-991b-8ad3f70beb72.jpeg align="center")