Re: No quite wizadry but.../ Percussive Maintenance
Not apocryphal at all. There was a series of IBM disk drives (back around 1993-4 I think) where some of the internal rubber in the seals degraded. It was fine when the disk was spinning, but if the disk was powered off, the tiny fragments or rubber would land on the platter, and then get stuck in the heads leading to dead disks.
We had a couple of servers where multiple disks in the RAID had failed, and the fix was to drop the disk (sideways, on it's long edge) against the disk from about 3" high, two or three times, before putting it back in the server and see if it span up. Following that, we had the IBM engineer on site for about 3 days swapping the disks out one at a time on the servers (IBM only replaced the disks, not the RAID mounting cage). An exceedingly dull job for him!