Uncovering a faulty HDD

Helped a dealer troubleshoot one storage box. Apparently smartmontools gave a clean bill of health...WD diagnostics also did not flag it (a rare combo) though there were plenty of vnode_pager_putpages on the console. It took a  make buildworld to actually uncover LBA ABRTs, so that helped in identifying the faulty HDD. Off to RMA. Thanks to ZFS RAID-Z1, no data was lost or corrupted.