I have a Mac Pro (or Xserve) with an internal Apple RAID card. Why isn’t Drive Scope able to read the SMART information of the drives connected to the Apple RAID card?

SMART data relies on the hardware passing that data directly. However, RAID controllers simulate their drives to the system as logical (virtual) disks. Because they are logical disks, hard drives connected to Apple RAID cards do not provide SMART data to macOS, and so are unsupported.

If you want to know the SMART status of each of the individual hard drives that make up your hardware RAID, use Apple’s RAID Utility (/Applications/Utilities) or Apple’s System Information application (/Applications/Utilities) and select the Hardware RAID option in the Hardware disclosure view for the SMART status information. However, the SMART status reading from either of these utilities is a SMART overall health self-assessment result and doesn’t provide the predictive ability that Drive Scope does.