I have created one DocumentDB cluster in AWS with two instance running in it, but I need to know the exact storage which will be used for storing the data and also how AWS charge for one cluster.
When you provision an Amazon DocumentDB cluster, you don’t need to specify how much storage or I/Os you need for your cluster. Amazon DocumentDB uses a unique storage system that automatically scales from 10 GB up to 64 TB of data per cluster in 10 GB increments.
Storage is at the cluster level, which means all your instances share the storage. You can view how much storage are you using my monitoring the VolumeBytesUsed metric in the Monitoring tab of your Amazon DocumentDB console. Storage in DocumentDB is priced as low as $0.02 per GB/month (prices may vary across AWS regions). Details here - https://aws.amazon.com/documentdb/pricing/. To how much you are paying for storage, you can also go to the AWS Billing console and view the details of your DocumentDB bill