Four years of NAS drives: the health report

The NAS turned four this summer. Time to dump SMART data across all drives and see whether the anxiety has been justified. Short answer: mostly not, but one drive earned its retirement.

Across the four 4TB mirror drives and three SSDs: two drives each logged a handful of reallocated sectors in year two, then stabilized. One HDD showed rising pending sectors last spring and was swapped out before it failed. Zero catastrophic failures.

The interesting numbers are boring ones: power-on hours per drive between 30,000 and 35,000, load cycles well within spec, temperatures sitting at 34-39C thanks to the fan curve work.

The meta-lesson stands: SMART is a smoke detector, not a crystal ball. It caught one slow failure early. What actually protects data is the mirror, the off-site copy and the quarterly restore drill -- in that order of importance, reversed.