I have configured a RAID 1 with two G-Tech 4t drives on my iMac (OS X El Capitan 10.11.6). The RAID is mounted and accessible, but one of the drives has stopped flashing when writing to the RAID. Both were flashing when I started. I am concerned that the drive is damaged. I cannot access it apart from the other drive with Disk Utility. I need to know how to evaluate the drive and repair it if it’s damaged.