Issue with disks spinning down during rescue

[Eirik Øverby]

Hi,

This is in fact a success story (see end of message), but: I was trying to rescue data 
from a Quantum Fireball SCSI drive today, and experienced a peculiar problem. After lots 
of "interesting" noises and a few dozen MBs into the rescue process, the disk 
decided to spin down. It was still attached to the bus. The weird part is that ddrescue 
kept getting data from it - presumably zeroes? and though all was well. This also applied 
during phases 2-5 when it went back to read the bad/skipped parts - I ended up with a 
100% recovery rate but most of the result was obviously empty.

I was not using any special options to ddrescue except -r1. I did _not_ operate 
in direct IO mode on the first pass - I'm not even sure it makes a difference.

Platform: FreeBSD 12.1. ddrescue version 1.25. Controller: Adaptec 2940U.

I'm not even sure who's to blame here, though I would be very surprised if the 
CAM subsystem on FreeBSD would return data unless it received said data from 
the bus/device.

I did manage to recover most of the data on the drive by re-running ddrescue to 
create a new image, with the -d and -R options and a couple of re-runs. The 
spin-down did not occur again. I ended up with about 4k bad data, not bad for a 
drive that has not had power for about 18 years.

Has anyone seen such behavior before?

The resulting image was written to an SD card and, with a scsi2sd card, booted 
AmigaOS on an old Amiga 4000 without further issues :)

/Eirik