Well, I'm not sure. I have been looking at the source code for
format. It looks like the format program issued a SCSI Reserve command to the disk via a uscsi ioctl() call and this failed. Previous to this, the format program issued a SCSI Inquiry command which succeeded. Looking the
SCSI-2 Standard, it does not look like the Reserve command will actually do I/O. And you can do an Inquiry while another Inititator has a device reserved.
So I am guessing that somehow the system thinks that the drive is reserved. This could be legitimate if the SCSI chain connected to two hosts in a cluster or something like that. Maybe the drive just is in a confused state... a power cycle is susposed to reset any reservations. Maybe the drive is broken is some way that makes it always look reserved. Few of us actually ever use the "format" menu item in the format command, so maybe it has a bug.
But I would try some other stuff before I conclude that the drive is bad.