How does SoftRAID determine how many hours a disk has been used?

SoftRAID uses SMART to ask a disk how many hours it has been used. Disks which support SMART are on Thunderbolt, SATA, SAS and Fibre Channel buses. Disks which don’t support SMART will say “SMART status: test unavailable” in the expanded part of the disk tile in the SoftRAID application main window.

For disks which don’t support SMART, the SoftRAID driver maintains an hours of use counter which it updates every time your Mac is shutdown or volumes on the disk are unmounted. This counter is stored on the disk itself and is still valid if you move the disk to a different Mac. SoftRAID will even restore this counter to its correct value if you initialize the disk a second time.