What is the difference between boot disk and data disk in GCP (especially AI platform)

I am using the AI platform of GCP. I need to choose the size of a boot disk and a data disk during the creation of the VM instance please see this attached image.

I have 500GB of data to be analysed in the AI platform. Should I choose more than 500GB disk size for both the boot disk and the data disk, OR is it enough to increase only one of the disk sizes (e.g., data disk size to be 500GB)? I am also not sure about the different roles between boot disk and data disk. Thank you.

When you create a new Notebook instance using Notebooks API, the API will create a VM with 2 disks:

1. Boot disk where the OS/libraries/initialization scripts live
2. Data disk which is mapped to /home/jupyter folder.

The reason to do this is to support Upgrade, where you can upgrade your VM by replacing the Boot disk with a new OS while preserving your data. To answer your question, I would allocate space in data disk.