i am new to Elasticsearch and still learning it . can i please how to calculate the number of shards and replicas required for an index ? i now that number factors should be considered but i am kind of confused after reading articles on the internet because some say to use 40% of data node capacity while others use the JVM heap size for calculation shards. For example, i have 9 node cluster with 10GB storage per node and i want index 50 GB of data and JVM size is 32GB. how many shards and replicas do i need ? what is the best practice ?Any detailed explanation would be really helpful .