The sleep mode on your Macintosh helps your computer conserve energy by powering down certain parts of the computer’s hardware while not in use. If you are transferring a large amount of files through your USB drive, you can adjust the settings in the “System Preferences” to put parts of your Mac to sleep while keeping your USB drive active. While sleeping, the display will go dark but the USB drive will continue to send and receive data from your hard drive. Tips Writer Bio
