Amiga 1000 SCSI drive error just now...

[Zac67]

If a write gets interrupted (power loss, guru, reboot) the filesystem is flagged as dirty. On the next bootup it'll get validated which may fail (as in your case apparently) and leaves you to the mercy of disksalv (or possibly some other tool revalidating the disk). I'd recommend backing up the partition and then trying disksalv. If all fails you may need to reformat and restore from backup.

More advanced filesystems don't have this weakness but Kick 1.3 probably limits the options...

[Zac67]

So -- a guru during a write can cause a disk to be come unvalidated. And in order to fix it (well, with DiskSalv), you need a 2nd hard drive or partition of >= size on-hand?

Worst case - yes.

I know more recent AmigaDOS versions auto-revaldiate on boot.

All do, but there are problems the autovalidation fails to fix.

Quarterback Tools have worked pretty nicely for me - but there is some risk involved and precious data should be backed up (anyway).

In these days where HDDs <1 gig are considered tiny and can be had for (next to) nothing there's no real excuse for not backing up...