macOS Sierra: Check whether a disk is about to fail
You can check the health of many disks using Disk Utility. Many disks include Self-Monitoring, Analysis, and Reporting Technology (S.M.A.R.T) hardware, which lets a disk test itself for potential problems.
In Disk Utility, select the disk in the list at the left, then click Info.
If you see a message saying the disk has a fatal hardware error, the disk has an irreparable hardware problem that can’t be fixed by Disk Utility or any other utility that repairs software problems. Back up as much of the data on the disk as possible, then replace the disk.
If you don’t see a message saying the disk has a hardware error but you still have problems with the disk, you can try to repair it with Disk Utility.