Synology DS925+, two failed drives: 99% recovered
A company near Mons kept all its project folders on a Synology DS925+ NAS with no backup at all: four 4 TB Synology HAT3300-4T drives in SHR-1. A first drive failed, and its rebuild stopped at 0.4%. Shortly after, a second drive was ejected and the volume went offline. Synology support tried reinstalling DSM, failed, and closed the ticket. The company's IT partner then brought us the three remaining drives. One of them reported SMART FAILED, with 13,040 pending sectors, and was reading at under 1 MB/s.
Every drive was imaged first; all later work ran on the copies. Analysis showed two four-member mdadm RAID 5 arrays stacked under LVM. Assembly failed at first: the drive order had been changed during earlier attempts, and the exact position of each member had to be worked out. On the failing drive, head 3 (of 4) was reading very poorly. Rather than wear it down until it died, we opened it in the cleanroom, replaced the head stack with a donor set from our own stock, and imaged the drive with PC-3000. The 2026 folder was the most urgent, so it came out first.