|Understanding the architecture / Planning a cluster deployment|
Determining how much data your Cassandra nodes can hold.
To calculate how much data your Cassandra nodes can hold, calculate the usable disk capacity per node and then multiply that by the number of nodes in your cluster. Remember that in a production cluster, you will typically have your commit log and data directories on different disks.
raw_capacity = disk_size * number_of_data_disks
( raw_capacity * 0.9 ) = formatted_disk_space
formatted_disk_space * (0.5 to 0.8) = usable_disk_space