It is painfully slow to grant access to users/groups.
Be it via Portal or PowerShell.
4 hours to grant 100k objects on Data Lake Store.
There should be a server-side batch processing for this.
Shannon Lowder commented
At the very least, make the process Async so you can close the window and move on to other work, without causing the ACL job to stop!
Christian Sloper commented
This is very painful, indeed.