rescan causes offlined tape to reload

[G. Paul Ziemba]

mj at feral.com (Matthew Jacob) writes:

>My recollection is that when you 'eject' a DLT, unless you operate the 
>handle, or it's part of a changer unit that does it for you, any 
>subsequent Test Unit Ready will reload it.

>Other than that, there are couple of candidate changes in the XPT layer 
>in the time frame you talk of which may be inducing this behavior. Any 
>way you can get a trace of the SCSI commands sent?

Hmm. The same drive did not reload the tape upon rescan before I
upgraded to FreeBSD-stable from Jan 11, so I do not think Test Unit
Ready is causing it.

I rebuilt the kernel to set CAMDEBUG. The kernel and userland are
still the code from FreeBSD current as of 2011-Jan-11.

It looks as if "camcontrol rescan" generates a command specifically
to load the media (distinct from the TEST UNIT READY).

# uname -a
FreeBSD hairball.ziemba.us 8.2-PRERELEASE FreeBSD 8.2-PRERELEASE #0: Thu Jan 20 20:28:21 PST 2011     root at hairball:/usr/obj/usr/src/sys/GPZ-110111-camdebug  i386

# camcontrol debug -c 0:4
Debugging enabled for 0:4:-1
# camcontrol eject sa0
Unit stopped successfully, Media ejected

Jan 20 21:07:26 hairball kernel: (pass2:sym0:0:4:0): LOAD UNLOAD. CDB: 1b 0 0 0 2 0 

# camcontrol rescan all

Jan 20 21:08:40 hairball kernel: (probe4:sym0:0:4:0): TEST UNIT READY. CDB: 0 0 0 0 0 0 
Jan 20 21:08:44 hairball kernel: (probe4:sym0:0:4:0): LOAD UNLOAD. CDB: 1b 0 0 0 3 0 
Jan 20 21:09:34 hairball kernel: sym0:4:control msgout: 80 6.
Jan 20 21:09:34 hairball kernel: (probe4:sym0:0:4:0): TEST UNIT READY. CDB: 0 0 0 0 0 0 
Jan 20 21:09:34 hairball kernel: (probe4:sym0:0:4:0): INQUIRY. CDB: 12 0 0 0 24 0 
Jan 20 21:09:34 hairball kernel: (probe4:sym0:0:4:0): INQUIRY. CDB: 12 1 0 0 ff 0 
Jan 20 21:09:34 hairball kernel: (probe4:sym0:0:4:0): INQUIRY. CDB: 12 1 80 0 ff 0 
Jan 20 21:09:34 hairball kernel: (probe0:sym0:0:4:1): INQUIRY. CDB: 12 20 0 0 24 0 
Jan 20 21:09:34 hairball kernel: (probe0:sym0:0:4:2): INQUIRY. CDB: 12 40 0 0 24 0 
Jan 20 21:09:34 hairball kernel: (probe0:sym0:0:4:3): INQUIRY. CDB: 12 60 0 0 24 0 
Jan 20 21:09:34 hairball kernel: (probe0:sym0:0:4:4): INQUIRY. CDB: 12 80 0 0 24 0 
Jan 20 21:09:34 hairball kernel: (probe0:sym0:0:4:5): INQUIRY. CDB: 12 a0 0 0 24 0 
Jan 20 21:09:34 hairball kernel: (probe0:sym0:0:4:6): INQUIRY. CDB: 12 c0 0 0 24 0 
Jan 20 21:09:34 hairball kernel: (probe0:sym0:0:4:7): INQUIRY. CDB: 12 e0 0 0 24 0 


-- 
G. Paul Ziemba
FreeBSD unix:
 9:21PM  up 33 mins, 5 users, load averages: 0.11, 0.09, 0.08