An Azure Data Lake Analytics Unit, or AU, is a unit of computation resources made available to your U-SQL job. Each AU gives your job access to a set of underlying resources like CPU and memory. Currently, an AU is the equivalent of 2 CPU cores and 6 GB of RAM. As we see how people want to use the service, we may change the definition of an AU or more options for controlling CPU and memory usage.
How AUs are used during U-SQL Query Execution
When you submit a U-SQL script for execution, the U-SQL compiler parallelizes the U-SQL script into hundreds or even thousands of tasks called vertices. Each vertex is allocated to one AU. The AU is dynamically allocated to the task and released once that particular task is completed.
I appreciate the ADL team’s transparency in how they define a unit. It’s much nicer to be able to tell someone that an AU is 2 CPU cores + 6 GB of RAM, rather than saying it’s some fuzzy measure of CPU + memory + I/O which has no direct bearing on your operations.