Multi tenant Elasticsearch deployment - storage usage

Hello,
I have a multi tenant environment where the indexes are shared between tenants.The tenant data is secured using filtered alias .
But I need a way to track the storage used by each tenant in order to move their data
To their own dedicated index . I am unable to figure out how to get the storage size used by each tenant to be able to make the decision .
I can get the number of documents but not the storage size . This is critical and I need a solution if there is one available .

You might be able to get the total size of raw documents for a user through the mapper size plugin and use that to estimate portion of index storage used. It is not accurate but I am not aware of any other way to do it.