On a Mac OS10.11.5 the G-Speed Q RAID 5 suddenly was acting up. Noticed a drive was dark - no light on it - we have had issue with this drive before. Shutdown the computer and restarted and got an error that the “Disk is not readable” and it would not mount. Shut down and restarted both the drive and the computer. All lights on the drive came on as usual, but same error. The drive shows up in the Disk Utility.
So, I have replaced the drive that was unlit initially and problematic in the past…
UPDATE - Rebuild is complete and the drive still will not mount on the computer. Still says it is unreadable.