– Under Format: select Mac OS Extended (Journaled) – Select Options… and select GUID Partition Table – Select Partition Layout and then choose 1 Partition – Select the USB disk in the left pane and select the Partition tab If you are using Disk Utility under OS X Yosemite or earlier:
– Config > Serial ATA (SATA) > SATA Controller Mode Option > AHCI – Config > Power > Power On with AC Attach > Disabled