You want to make sure that the media files go to the drive(s) that you want when one becomes full, rather than Media Composer simply selecting the drive that happens to have the most free space
You have a large amount of media to capture but there is not one single drive that has enough space
Making a Drive Group is especially helpful when you want to leave the Capture process unattended
Open the Tools menu | Capture Tool.
Click on the Drive Selection menu. It's located directly below the Bin Selection menu and the Resolution Selection menu (refer to the next screenshot).
A dialog window will open, listing all the available drives.
Press cmd/Ctrl and click to select your desired drives.
Press the OK button.