For the below VM resource spec (1 for Cassandra and 1 for elastic), what will be the maximum SSD disk size that can be loaded for storage? And what will be the usable storage vs actual storage?
CPU: 1x16 core (10K passmark), RAM: 64 GB, OS: Linux Ubuntu LTS
It's hard to put 1 number on this as is has to many dependencies. Below you can find a general number for both databases.
Depending on how you configure it, as standalone Cassandra, or Cassandra Cluster with 1 node the data is saved a little different. However for this we follow the general rules from DataStax Cassandra, this to have a maximum of 2/3 TB per node in a cluster.
On the disk you should have space left same as the biggest table on your system. For example if you have lot of average trending, 400GB, then you need at least 400GB of free disk space so Cassandra can compact your data.
more information can be found here: https://docs.datastax.com/en/ossplanning/docs/oss-capacity-planning.html
Here we follow the recommendations from ElasticSearch itself, with the configuration of the CPU and memory, this would mean a maximum disk of 1.9TB.
For the usable space, this is almost the whole disk, as Elastic has a different way of handling the data.