HOW TO GIVE A DRIVE A HEALTH CHECK

OPEN DISK UTILITY

01 Disk Utility lives in Utilities within the Applications folder. As usual the quickest way to reach it is to press Cmd+Spacebar to open Spotlight and start typing its name. Its sidebar shows all the drives connected to your Mac.

VIEW DEVICES/VOLUMES

02 By default, you see ‘volumes’, logical spaces for storing files. If you want to see which physical drives they’re on and those drives’ structures, pick View > Show All Devices (or press Cmd+2; Cmd+1 shows volumes).

YOUR STARTUP DISK

03 Whether your startup disk is an internal or external drive, selecting it on the left dims out the Erase, Restore, and Unmount options. You can run First Aid, but repairs might need Disk Utility use in macOS Recovery.

RUN FIRST AID

04 On other drives, First Aid just asks for confirmation before starting checks, which can take a minute. It’ll automatically repair any minor issues that it finds, and warn you if any problems are found that it can’t fix.

DISK PERMISSIONS

05 Until OS X Yosemite, there was an option to verify disk permissions to clear up problems such as changes to macOS failing to ‘take’ or apps not opening. These don’t occur now; macOS is meant to deal with them as it goes.

TIME TO REFORMAT

06 If First Aid can’t repair errors on your startup disk. For any other drive, select an empty drive and use Restore to copy its contents. Erase the problematic drive and try using it, but watch out for failing health.